ONlwSG

flathadh f. *[ˈfɫ̪a(h)əɣ] is apparently attested only in the anonymous poem ‘Tha ghaoth ’n Iar cho chaithreamach’: 

A poem in praise of Ailean Dòmhnallach (Allan MacDonald), chief of Clanranald, on his and his brother Raghnall’s departure for the Battle of Sheriffmuir in 1715 (Tobar an Dualchais^˄: 109109, Pàirt 1). On p. 121 of NLS’s downloadable copy of An t-Oranaiche (Mac-na-Ceàrdadh 1879), from its Matheson Collection, a pencilled footnote against line 3 (Bha Ailein a’s Rà’ull ann) reads, ‘i.e. Allan MacDonald of Clanranald and his brother Ranald as they left South Uist for Sheriffmuir (Kill. MSS.).’ The reference to the Kill[earnan] MSS (Thomson 1983b, 165; NLS MSS 3781–3784) has not been pursued.

Nàmhaid geòidh a’s cathain thu, | Ròin mhaol ri taobh na flathadh thu: | Bidh ’n dòran-donn an tathunn leat, | ’S bidh abhag air a lorg (‘you are the foe of (the) goose and gander, 

Literally, ‘of goose and of Barnacle goose’.

of (the) sleek seal beside the water; you pursue the otter, 

With (ann) an tathunn ‘in hunting, pursuing’, i.e. ‘being hunted’; cf. SG tathann, tabhann, tafann: ‘bark, barking’ (Dwelly 1911, s.v. tabhann), ‘nagging’ (Wentworth 2003, s.vv. go (on at), nag), ‘urging, pressing’ (McDonald 1972, s.v. tathann), ‘chasing (as hounds), urging’ (Faclan bhon t-Sluagh^˄, s.v. tafann), cf. EG tafann ‘hunting (with dogs), pursuing, chasing out, barking (usually of dogs – perhaps the original meaning)’ (≈eDIL^˄).

and a terrier brings it to ground’) (Mac-na-Ceàrdadh 1879, 120–23: 121). Henderson (1910, 144) derives flathadh in the sense ‘sea (properly flood)’ from Norn [sic] (Shetland) flo, 

Jakobsen 1928, s.v. flo: [flō].

(Orkney) flow, 

SND^˄, s.v. ¹flow: ‘a wet peat-bog, morass, swamp; an arm of the sea, a bight, channel or haven where there is deep water or strong flowing tides’.

from ON flói ‘a wide, shallow pool of water; firth’ (NO); McDonald (2009, 354) considers the derivation uncertain.

An accusative/dative ON fló (a contraction of *flóa) would normally be expected to yield SG *flò. In the context of the poem, flathadh is in the genitive, and it may simply be the genitive of SG flaith 

Dwelly (1911) lists †flaith f. ‘milk’ and †flaith m. in the sense ‘strong ale’ separately.

(EG flaith ‘liquor, esp. ale or beer’ (eDIL^˄)), 

EG flaith is possibly the same word as EG laith ‘liquor’ (SG laith), but with prothetic f- under the influence of flaith ‘lordship etc.’ or by association with EG finn ‘milk’ (eDIL^˄).

used as a kenning for the sea. EG flaith ‘liquor’ is a feminine ā-stem (eDIL^˄), with genitive flaithe, but Ir. flaith ‘idem’ is a feminine i-stem, with genitive flatha. SG (gen.) flathadh shows final -dh closing an otherwise open syllable in -a, a feature of a number of Scottish Gaelic dialects, including those from Harris to Barra (Borgstrøm 1940, 178).