As in “Planxty Noel Hill” or “Planxty Morgan Mehgan”?
No idea, thought he was just some fellow who played music 
Never mind. I should have checked dictionary.com before I posted.
Not to mention a dear, departed music group. Ah, Planxty, we hardly knew ye.
RR
IIRC the planxty is also the song equivalent to an ‘ode to personX’’ … they are dedicated to a specific person and the music should remind the writer of some facet of the person it is dedicated to/named for. A friend of mine has written planxtys to several exboyfriends. I can even sort of tell which one goes to which person=)
They’ve reunited actually.