The seal of Scone depicting the inauguration of Alexander III in 1249. Contemporary accounts identify the people involved including the King's poet reciting / declaiming / chanting /singing (take your pick), the royal linage from a velum scroll held in front of him. Accompanied as was the custom by the harper squatting on the ground behind him in a playing position that Mary Rowland found was consistent with the wear marks on the Trinity College Harp when she played it at the British Museum while it was undergoing conservation in 1961.
Starting with the earliest uses of the word the presence of the ‘P’ indicates it was a loan word into Gaelic. According to the ‘Bible’ of the Irish Language, the Royal Irish Academy Dictionary, it is derived from the Latin word ‘portus’, meaning a place, spot or locality. Following a considerable number of column inches tracing the variety of meanings derived from that original ‘loanword’, for example a place by the shore to unload ships, being a ‘port’ or a term for an entrance or gate, at the end is a short paragraph on the word’s musical use. 
Described as ‘late’, it gives a few examples the earliest of which is Keating‘s Foras Feasa ar Eirinn. Written circa 1630 he uses port in most of its meanings throughout his work, but only once in the musical sense which in the quote in the dictionary refers to the mythical tale where the harper Craiftine was sent to France to play to Maon and thereby entice him back to Ireland. Another of the examples also falls into a similar scenario where, as a composite word ‘gallphoirt’ it translates as ‘foreign tunes’. From then it is not until after 1800 when in Arthur O'Neill's memoir and Bunting‘s manuscripts some named ports appear all clearly having a Scottish provenance and including one copied by Bunting from a published collection of Scots tunes by Donald Dow.
Turning to Scotland it is possible, albeit not conclusively, to make some observations. The evidence is based on the small number of tunes called ports, the earliest contained in music written for the lute family of instruments. Their names divide into two groups, one which features placenames, including the earliest, Port Ballangowne, along with Athole, Lenox and Gordon, the latter a family name which owes its origin to a placename, south of Edinburgh and about 12 miles north of Melrose. Although some of these names are derived from Gaelic, they had long been part of a general Scotland wide geographical lexicon so not in themselves strong evidence of a purely Gaelic origin. Indeed, it is noteworthy that the combination of ‘port’ linked to a placename is reflective of the original use of the loanword in the R.I.A Dictionary.
When the second group of tune names are considered, they clearly reflect the Scots language with no indication that they have been translated from Gaelic. In one of them ‘port’ may not even be meant in a musical sense as ‘the Horseman's port’ can also interpreted using another of the dictionary uses of ‘port’ as the ‘Horseman’s entrance or gate’. What is clear when looking at the ‘names’ in both groups as well as the locations of the early source manuscripts, geographically their distribution in Scotland leans well towards the South and East of the country. An area which at the period the tunes called ‘ports’ originated could at best be described as Scots speaking but although Gaelic was in retreat, it still had some remaining presence. In other words, a linguistic and cultural melting pot.
The earliest evidence of the use of ‘port’ in a musical sense comes from a poem, circa 1500 in the Book of the Dean of Lismore.  It is on a man who has lost his voice and therefore both voice and harp are silenced. A reflection of the fact that the early use of stringed instruments was to support vocal delivery and therefore, the poet did not envisage the instrument being played on its own. As the late John MacInnes put it, when referring to this poem, it was "The only Scottish poet…. who was certainly not a native of the area dominated by the Lords of the Isles is the only one for whom the compilers saw fit to record his place of origin, namely, Duncan Mor from Lennox." 
The Towers is one of the oldest buildings in Dysart built according to the date on the Door lintel, in 1589. It would therefore have been very familiar to Margaret Wemyss compiler of the lute manuscript which contains some of the first tunes noted as ‘ports’. She lived on the edge of Dysart and at that time given the height of the Towers it would have been visible from her home. The towers also illustrates how the term ‘port’ had presumably from the original Latin, had entered the Scots Language as a description of a street which leads into a town. The Towers sits on the corner of Quality Street and the East Port.
For further images of The Towers, please see the image at St. Andrews in which one can see the East Port name. The Canmore pages of the National Record of the Historical Environment contain several images of The Towers.
Staying with Lennox but moving back to circa 1200, a monk called Adam of Lennox was the Porter (door keeper) of Melrose Abbey. He was said not to have slept instead spending his time playing the harp and "singing songs called Motets" in honour of the holy mother. In 1252 Adam of Lennox moved to become Abbot of Balmerino in the north of Fife. This was only 20 miles from a property now known as Balvaird, which was restored to the late King Alexander III‘s harper Elyas on the orders of Edward I in 1296. Alexander III had died in 1286, but just as the position of the royal harper would have been hereditary, so too their lands and the harper involved with the inauguration of Alexander at Scone (also just 20 miles from Balvaird), in 1249 probably had the same landholding. 
Fife also figures prominently when looking at the four 17th century music manuscripts which include ‘ports’. The Skene MS comes from a family who lived at Hallyards which is now somewhere under Edinburgh Airport, but which would have looked north across the Firth of Forth towards Fife and the lands of the Earl of Wemyss. The Earldom of Balcarres is next door to Wemyss just leaving the Straloch MS from Aberdeen as the outlier, albeit another source firmly placed in ‘Lowland’ Scotland. The Straloch MS is also problematic having not been seen since 1845 and with several contradictions including the possibility that it had been turned over and written from both ends; a common practice at that time but with further implications for dating some of the contents.
Looking at some of the named tunes there is also a pull towards the same geographical area. The family who held the Earldom of Balcarres were called Lindsay and another branch of that family held another major lowland Scottish earldom, that of Crawford, suggesting a connection to ‘Port Jean Lindsay’. Another tune with two different names, ‘Port Robert’ and ‘Port Priest’ may be for Robert Stewart second son of the 11th Earl of Lennox who followed a clerical career and in 1563 obtained the Priory of St Andrews. Although a lot of this evidence is indeed circumstantial the overall picture does not reflect the popular image of the ports as ‘highland harp music’ but instead relates them to the musical world of the royal court and courtiers, with two of the Stewarts favourite royal palaces, Linlithgow and Falkland also falling within that same geographical area. It was though a musical world which came to an end with the loss of its focal point when in 1603 James VI left Scotland for the English throne.
 Watson, W.J. ed. Bardachd Albannach- Scottish Verse from the Book of the Dean of Lismore (1978)
 MacInnes, J. Gaelic Poetry and Historical Tradition. In The Middle Ages in the Highlands. The Inverness Field Club. (1981), p. 147.
 Bannerman, J. The Residence of the King's Poet. Scottish Gaelic Studies. (1996). Vol XVII. pp 24 - 35.