v1.0
Published 01/10/24
-port , e.g. (Lewis) [pɔʈ], (Uist) [pɔɍs̪t̪], (Skye) [pɔɍt̪].
Cf. the reflexes of SG sagart ‘priest’ in SGDS Item 727.
McDonald (2009, 353) notes that MacBain (1895, 231) and Fraser (1979, 23) derive the Scottish Gaelic place-name endings -port, -fort and -fhurt from ON fjǫrðr m. ‘firth, bay’, but that MacBain (1911) derives SG port (not as a place-name element) from Lat. portus, concluding that ‘[a]s a semantic unit (rather than just onomastic) this is likely a Lat[in] loan’.
The name forms of several sea lochs on the west of Scotland are spelt or have at some time been spelt with final -port: SG Caolasport, Knapdale NR764769, cf. Blaeu (1663, probably surveyed 1583–1601): Loch Cheulispurt, Loch Cheulis purt; SG Èireasort, Lewis NB352308, cf. Blaeu: Loch Erisport; SG Eufort, North Uist NF855633, cf. Martin (1703, 56, 58): Loch-Eport (the name form also occurs in Skye (Forbes 1923, 186)); SG Thàrport, Skye NG368344, cf. Blaeu: Loch Herport; SG Sgiobort, South Uist NF820388, cf. Blaeu: Loch Skibbort, OS 1843–82 Loch Skiport; SG Sgrèasort, Rum NM409995, cf. Blaeu: Loch Screspoirt; SG Snìosort, Skye NG375573, cf. Monro 1549, No. 132 in Munro 1961: Loch Sneisport; and SG Suaineafort, Loch Sunart NM666613, cf. Gillies 1906, 83: Suaine-port, OS 1843–82: Rubha Suainphort. The Gaelic reflexes of these names derive from Old Norse originated sea-loch names ending in -fjǫrð acc. The Old Norse fricative f- is retained in SG Suaineafort (Suainphort), where it coincides with the initial of SG (lenited) phort ‘landing place; harbour’. In some instances, the fricative develops into SG p (particularly after s, 
For defricativisation after s, see Ó Maolalaigh 2016, 91–92.
although subsequently sp is usually reduced to s), presumably also via folk etymology in association with SG port ‘landing place; harbour’.
For further discussion of these and other fjǫrðr-names in Gaelic, see Cox 2007b, esp. 74 ff.
The element surviving as -port etc. in these names, then, is a phonetic or folk etymological reflex in Gaelic of ON fjǫrð, but not evidence of the Old Norse word having been borrowed into Gaelic.
McDonald (ibid.) assigns the sense ‘bay’ to final -port, -fort and -fhurt. However, while to their Gaelic-speaking users the onomastic meaning of the Old Norse loan-names in question may be ‘a particular bay’, as functioning place-names they hold no lexical meaning in Gaelic.
SG port ‘landing place; harbour’ is a loan-word from Lat. portus ‘harbour, port, haven’.
(Cf. the development of SG port in the compounds longart etc. (EG longphort lit. ‘ship-place, i.e. harbour’, with EG long ‘ship’; Watson 1926, 493–95; 1978, xxix) and ceannard (EG cennphort ‘capital → leader, chief’, with EG cenn ‘head → principal’; Watson 1978, ibid.; Ó Baoill 1990, 141–42).)