v1.0
Published 01/10/24
bàirlinn f. [ˈb̥ɑːɭiɲ] 
In Iain Lom, cf. the rhymes eàrrlainn : bàirlinn : bràghad (MacKenzie 1964, 102, line 1328).
‘rolling wave, or sea, a high sea (Armstrong 1825); surge, billow, rolling wave (HSS 1828); rolling wave, billow (MacBain 1911); enormous wave, billow (MacLennan 1925)’.
MacBain (1894a, 618) records Cameron’s etymology of SG bar [= bàr] ‘the sea’ from ON bára f. ‘wave, billow’. The form bàr ‘sea’ may be from HSS 1828, 
Dwelly 1911 has †bàr m., gen. bàir and bàrach, ‘the sea’ and †bair [sic] f. ‘wave; the sea’.
but it is likely it is for bàrr (EG barr; s.v. bàrr) and ‘sea’ is likely to be an extension of its basic meaning ‘the top of something’. Nevertheless, MacBain (1896) derives bàirlinn from ON bára ‘wave’ + SG linne f. (EG linn, acc./dat. linn, linni, linne ‘pool, lake; sea, ocean’).
So Henderson (1910, 142); MacLennan (1925); Stewart (2004, 408); McDonald (2009, 340; 2015, 141); Ó Muirithe (2010: ‘+ Irish linn’)).
HSS (1828: bairlinn [sic]), however, suggests a derivation from bàrr + linne (EG barr + linn). SG barr, with a short vowel (before lengthening took place before the heavy cluster -rr) occurs in a number of closed compounds, e.g. barrad m. ‘uppermost layer of peat’ (+ fàd m., s.v. bàrr), barriall m. ‘shoelace’ (+ iall m. ‘thong’) and barrdhias f. ‘point of a sword’ (+ dias f. ‘ear of corn’). In the case of the closed compound *bairrlinn, lengthening occurs before the heavy cluster -rl, 
Cf. the development of the prefix ur- in uireasbhaidh, urchasg and ùrlabhairt (Cox 2017, 14, §11(iv), and 376).
although bàirlinn may have been written given the propensity to write bàr for bàrr, but also because *bàirrlinn and bàirlinn would formally not be distinguishable phonetically.