Hmm, yes, this thread clearly needs a specialist consultation, but my specialist knowledge is somewhat limited, and I felt that I couldn’t add much more than speculation, and that while the doctors differ the patient might die.
For what it’s worth, here is my modest contribution.
Some of the issues are discussed in Beandán Breathnach’s book, but I haven’t got it to hand.
Ríl is indeed the word that you’re most likely to hear among modern speakers of Irish, and it is no more than an Irish spelling of the English word. Contemporary Irish is so penetrated by English that in many cases an English word is freely used even where a perfectly good Irish word exists, and some constructions would not even be readily understood by a hypothetically “pure” Irish speaker unless he had learnt English. So, where a Dublin schoolboy of the 1950s/60s like myself would strive to use the idiomatically and lexically pure construction “Tá mo rothar á teannadh agam”, a contemporary native speaker even then would probably have said “Tá mé ag pumpáil mo bheidhcicil”, i.e. “I’m pumping my bicycle”. Maybe Patrick Pearse should have rolled over and gone back to sleep on Easter Snday morning 1916.
I remember reading, and it may have been in Breathnach, that “cor”, which means uneven, odd, anomalous, used to describe a reel, suggests that the default assumption was that a tune (port) should normally be in triple time (cf the use of a C which is in fact a broken circle to represent"common" time, whereas a circle, representing perfection, was apparently used in liturgical manuscripts to represent triple time, by reference to the Blessed Trinity). Port can mean any kind of a dance tune, but is also the normal word used in Irish for a jig. Fonn, which could be said to correspond to “melody”, is the word used for a slow air, though I don’t know if the qualification “mall” , (slow) is necessary or not.
As regards the hornpipe, it seems to be generally accepted to be an English invention (possibly because of association with Jack Tar), and I would normally expect an Irish speaker to call it cornphíopa. I’ve seen crannciúil in O’Neill’s, but don’t think it’s widely used. “ciúil” is not a standard suffix, and I know nothing about the etymology. Crann is primarily a tree, though it is also used for the mast of a ship.
There is a very helpful Irish scholar on Mudcat who trades as Philippa, and maybe we could summon her for a consultation here (assuming that she isn’t still mad at me for what I thought was a sweet diminutive of her name, until her reaction caused me to look it up in the dictionary Ach fágfaimíd sin mar atá sé). To be continued.
PS, you’re bringing me back a few years with your hapax legomenon, Pitchfork, old sport, though strictly speaking it’s something once said rather than once printed (or even written 
).
Indeed. Then again, this happens in any language and may in the end wind up being a healthy thing. Japanese for instance seems to be absorbing about 100 loan words (mostly, though not entirely, English) a week. In some situations it seems almost impossible to form a sentence in “pure” Japanese anymore. Consider the following, for example: