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lobhta and lobht 
Cf. Lhuyd 1700, 198 XXVII.62: a hay-loft ‘lôty feôr hirim [lobhta feòir thioraim]’ (Argyllshire), ‘lowt syy [lobhta saidhe]’ (Inverness-shire); MacDomhnuill 1741, 85: lotta-saoidhe; Shaw 1780, Mac Farlan 1795, MacFarlane 1815: lotadh.
Dwelly 1911: Wester Ross and North Uist; Faclan bhon t-Sluagh˄: North Uist and Skye; Borgstrøm 1941, 20: Skye; McDonald 1972, 167: South Uist; Wentworth 2003a, s.v. floor: Wester Ross.
Shaw 1780; cf. lobhta nan lìon ‘the moveable beam fishermen would stand on to shake nets’ (≈Faclan bhon t-Sluagh˄, s.v. lobhta: Scalpay).
Dwelly 1911; cf. fo lobhtaidh ‘below deck’ ([An] Dughalach 1829, 192); lobht a’ bhallaist ‘the flooring over the ballast in a fishing boat’ (Faclan bhon t-Sluagh˄: Scalpay).
Dwelly 1911; Wentworth 2003a, s.v. storey: Wester Ross.
Dwelly 1911.
E.g. Shaw 1780; Mac Farlan 1795; MacFarlane 1815; Dwelly 1911.
Cf. lotta-saoidhe [lobhta saoidhe] (MacDomhnuill 1741, 85); lobht an fheòir (Faclan bhon t-Sluagh˄: Kinlochourn).
Faclan bhon t-Sluagh˄: Lewis and Tiree; Ó Murchú 1989, 366: East Perthshire; cf. lobht an t-sobhail (Faclan bhon t-Sluagh˄: Nova Scotia), lobht an t-sabhail ‘raised portion of barn on which corn is stored’ (≈Faclan bhon t-Sluagh˄: Tiree).
‘Ann an cuid de phuirt air a’ chost a-sear bhiodh cùirearan a’ togail taighean mòra fiodha le mòran rumannan do chlann-nighean an iasgaich ... ’S e lobhtaichean a chainte ri na taighean seo’ (≈Faclan bhon t-Sluagh˄: Lewis) [‘in some ports on the east coast curers built large wooden houses with lots of rooms for the fisher girls ... They were called lobhtaichean’]; cf. ‘Each girl packed all her possessions ... into a wooden chest or “kist”, which also at times served as a wardrobe, a seat and even at times a table in the unfurnished wooden huts that were the girls’ accommodation at some of the fishing ports’ (≈The Angus Macleod Archive: The Herring Girls).
Faclan bhon t-Sluagh˄: Tiree; cf. lobhta poc ‘ceiling of sacking in a black house’, Lewis (ibid.).
The form SG Lobhta Coire is suspicious: *Lobhta Choire would be expected. Perhaps it is a gaelicised spelling of an anglicisation (Lota Corrie) of a Gaelic name *Coire an Lobhta ‘the corrie of the terrace’; cf. the parallel development in Eng. Harta Corrie < SG Coire Tharta.
SG lobhta is derived from ON lopt -[ɸt] nt. ‘air, space, sky; hole, opening; loft of loose boards in a barn; upstairs, attic’ (cf. NO) by Craigie (1894, 157: lobth [leg. lobht], lobhta), MacBain (1896; 1911), Henderson (1910, 215), Marstrander (1915a, 96, so also de Vries 1962), Borgstrøm (1937, 105; 1940, 168: or from Eng. loft), Oftedal (1956, 105: if not through Eng. loft; 1972, 117: probably from Old Norse), Matheson (in CG VI, 99), Cox (1991, 492; 2002a, 316; 2022, 448–49 fn 17) and McDonald (2009, 383). From a phonetic point of view, however, SG lobhta might also derive from early MScots loft, 
MScots loft > laft in the late 16th century (Aitken 2002, 100).
Original -[Ft] (where F = either the voiceless bilabial fricative + stop of ON -[ɸt] or the voiceless labio-dental fricative + stop of MScots -[ft]) yields a preaspirated stop in Gaelic (parallel with the historical treatment of post-stress geminate stops, e.g. EG *slatt 
Commonly written slat (eDIL˄, s.v.).
E.g. Lewis: /Lot(ə)/ (Oftedal 1956, 105), [ˈɫ̪oʰt̪ə] (Cox 2022, 448–49 fn 17); Barra: [Lɔhtɔ̆] (Borgstrøm 1937, 105; 1940, 168); Vatersay: [ɫ̪ɔʰt̪i] (Tobar an Dualchais ID 37118); Sutherland: ‘lobht’ (Grant 2013, s.v. loft); Wester Ross: [ʟoht] (Wentworth 2003a, s.vv. attic, floor, loft, storey); Skye: [Lohtə] (Borgstrøm 1941, 20); Kinlochourn: [ɫoxt̪] (Faclan bhon t-Sluagh˄); Islay: /ˈtohtə/ (Grant 1987 I, 205); West Perthshire: /ɫɔuxd/ (Ó Murchú 2021, 266); the Aird, Inverness: [ləuht] (Faclan bhon t-Sluagh˄, s.v. lobht: transcription only, but cf. (from the Aird) ‘leobht “a loft”; the o is a diphthong as in fowl; full palatal l’ (≈Barron 1974, 367). But note that in Gigha the preaspirate has been vocalised, yielding a diphthong in [lɔutə] (Holmer 1938, 185 and 56). Craigie (1894, 157) states the word is pronounced ‘lovt’, but this is a spelling pronunciation.
E.g. Kintyre: [ʟǫ’tə] (LASID IV, 196, Item 160 b, with a glottal catch following the short stressed vowel); East Perthshire: /ɫoˑud/ (Ó Murchú 1983, 366). Note that the preaspiration in (Arran) [ʟoʰṭə] (LASID IV, 196, Item 160 a) is exceptional in this regard.
With [u], cf. Lewis: [ɫu̜t̪] (Faclan bhon t-Sluagh˄); [ʟuhṭ] (LASID IV, 196, Item 160 e); Benbecula: [luhṭ] (LASID IV, 196, Item 160 d); Mid-Argyll: [ʟuxṭə] (LASID IV, 196, Item 160 c, also p. 227, s.v. lobhta); with [ɔ], cf. North Uist: [ɫɔtə] (Faclan bhon t-Sluagh˄).
E.g. Glengarry: [L(ou)hdə] (Dieckhoff 1932); the Aird, Inverness: [ləuht], with fronting (Faclan bhon t-Sluagh˄, s.v. lobht: transcription only, but cf. (from the Aird) ‘leobht “a loft”; the o is a diphthong as in fowl; full palatal l’ (≈Barron 1974, 367); Speyside: lowt syy [lobht saidhe] (Lhuyd 1700, 198: XXVII.62, s.v. hay-loft); East Perthshire: /ɫoˑud/ (Ó Murchú 1983, 366); and West Perthshire: /ɫɔuxd/ (Ó Murchú 2021, 266). For (Gigha) [lɔutə] (Holmer 1938, 185), see fn 15, above.
Early Modern Irish lota, 
eDIL˄: Stair Ercuil (c.1462–1473); the New Testament (O’Donnell 1602); the Old Testament (Bedell 1685).
eDIL˄: the Old Testament (Bedell 1685).
eDIL˄: Cín Lae Uí Mhealláin (1640s).
Dinneen 1927; Ó Dónaill 1977; LASID I, 160, records luta -[t]- in the west, lofta -[ft]- in the north and luchta -[xt]- in the south of Ireland.
MacBain (1896; 1911); Bugge (1912, 296); Marstrander (1915a, 96–97: (Donegal) lofta, (Kerry) lochta; so also Sommerfelt 1949, 234: lofta [Lautə], [Laftə], Donegal); and McDonald (2009, 383). For de Vries’s (1962) description of lofta and lochta as Old Irish, read Irish.
Note that Henebry (1898, 64) suggests that Ir. ‘lochta, Eng. “loft” was borrowed while -ft was still -cht. So “trough” still keeps its old pronunciation in Ireland viz. trȧc [sic]’. However, there seems to be no evidence to suppose that Eng. loft was ever pronounced with a velar fricative, and Ir. trach ‘trough’ may simply be a (relatively recent) borrowing from Scots troch ‘trough’ (SND˄, with a ~ o alternation, cf. Ulster Scots troch etc. (Macafee 1996, s.v. trough)).
Medial ft in (Ulster) Ir. raftan [rɑftɑn] ‘rat’ (Quiggin 1906, 110 §312; from Ulster Scots ratton ‘idem’, and still in use in Scots and Northern English, < OFr. raton (Macafee 1996)) and geafta [ɡˊɑftə] ‘gate’ (Quiggin ibid., see also LASID I, 38; from Ulster Scots yett, yeat, also in Scots, Northern English and South-Western English, < OEng. geat (Macafee ibid.)) is perhaps analogical and based on Ir. lofta and tobhta, q.v.
Cf. Ulster: laḃta (eDIL˄: Cín Lae Uí Mhealláin, 1640s); Rathlin: lafta [lɑftə] (Holmer 1942, 208); Donegal: [Lautə], [Laftə] (Sommerfelt 1949, 234); northern Ireland: LASID I, 160: Points 66, 68, 70–71, 76, 80–85.
O’Donovan’s Supplement in O’Reilly 1864: ‘close or field; croft’
In discussion, Marstrander (1915a, 97) notes that ‘shetlandsk tuchta = [Old Norse] þóttir’. The form tuchta is from the Orkney Norn ballad ‘Hildina’: Hægstad (1900, 9, 20, 37 §9, 65 §62.4) takes (stanza 34) tuchta to represent ON þóttir ‘(2 sg. past tense) thought’, although the form tuchta may conceivably have been influenced by Scots thocht [θoxt], (Shetland) [toxt] ‘(past tense) thought’ (SND˄, s.v. think).
Mx lout [løut], [laut] ‘loft’ (Broderick 1984 II) is generally derived from ON lopt also.
MacBain (1896, 1911), Marstrander (1915a, 96; 1932, 49, 265, so also de Vries 1962), R. L. Thomson (1963, 68) and McDonald (2009, 383).
Mx crout [krʌut] (Marstrander 1932, 131), [krøut] (Broderick 1984 II) is no doubt from Eng. craft. Mx shout *[ʃʌut], *[ʃøut] 
R. L. Thomson (1963, 68) remarks that Mx shout occurs in ‘the old Prayer Book’. The only surviving manuscript copy of Bishop Phillips’s 1610 Manx translation of the Book of Common Prayer is dated c. 1630 and contains (Psalm 104: 3) Mx shoutyn (Thomson 1953, 311, s.v. SHOUT), showtyn (Wheeler 2019a (diplomatic edition)) pl. ‘beams’; hence Broderick’s (PNIM IV, 21 fn 1) reference to (Phillips) showt.
R. L. Thomson (1963, 67–68) indicates that Mx gioot occurs in the Manx version of St John’s Gospel (Conaant Noa 1763), e.g. 4: 10 gioot Yee ‘the gift of God’; it also occurs in the 1748 Manx version of St Matthew’s Gospel (Wheeler 2019b), e.g. 8: 4 yn gioot ‘the gift’. However, the word already appears in Phillips’s c. 1630 Book of Common Prayer: in the Psalms, e.g. 68: 18 (pl.) giwtyn (Wheeler 2019a; also in 72: 10, where a gap left in the original is filled by (pl.) giwtyn, added in another hand (ibid.)); and in excerpts from the New Testament, e.g. Romans 6: 23 giût (Moore and Rhŷs 1895, 241 a 23), and 1 Corinthians 1: 7 giut (ibid., 268 a 7); the word for ‘gift’ in Phillips is otherwise toyrt or toyrtys (cf. Y Kelly 1866).
For the broad quality of the final of Mx gioot, cf. Jackson 1955, 16. For the alternation /au/, /ou/, /əu/ ~ /uː/ in Manx, cf. Broderick 1984 III, 74–77 §§10–16.
For Anglo-Manx laf, laft [lāf], [laf] ‘loft’, Moore (1924) compares Ulster Scots loft, laft and Scots laft; Anglo-Manx crof, craf [krof], [kraf] ‘croft’ and taff [taf] ‘thwart’ (ibid.) may have a similar heritage. Anglo-Manx lout [lout] ‘loft’, on the other hand, is taken to be from Manx (ibid.).
Derivatives: for SG (Barra) lobhtag, with the nominally diminutive suffix -ag, and (Vatersay) lobhtaidh, probably a normalised dative form of a dental stem (cf. Cox 2017, 101 §81(iii)(a)), see above.
Cf. SG tobhta, Ir. tota, tofta/tafta, tochta and Mx thowt, s.v. 1tobhta.