This once again lends credence to the concept that while there are thousands of tunes and thousands of lyrics out there, the lyrics are often the part of the song that survives. So many people have come across lyrics without a tune and because of the quality of the lyrics have "fit" them to another tune they actually know (I've done this in the past and a couple of times, when I've learned of the original tune, have likes the "fit" better.)When there are more than just 4 tunes in Irish music, it is more accurate to say that so many lyrics can fit into a surprisingly small number of tunes. Our folk group in Orlando often sings "Amazing Grace" to the tune "House of the Rising Sun" (actually we sing just about everything to that - we get rather goofy).
pax yall