Twisted "sister"

Will the wonders of Goidelic historical phonology never cease? Five months ago, I posted an insight into the development of PIE *swesor in Irish, namely that the lenited form was fiur in Old Irish rather than *shiur because of the effect of the *w. At the time, I had no idea what the modern Scottish Gaelic form was and when I came across it in one of Campbell's tales last night, it caught me quite by surprise.

It's piuthar. From what I can tell, the medial th is an archaic retention (found in the Old Irish genitive, for instance), but how to explain that initial? My guess is that when the Teuchters levelled this one out, they did it based on the lenited form rather than the radical one. That is, when faced with the puzzling alternation *siuthar <-> *fiuthar, they decided that the latter was really phiuthar, and thus what they had here was a straightforward lenition of /p/ rather than a screwy change of /s/.

This is why I love force of analogy. You'd be hard-pressed to find a series of exceptionless sound changes that would transform /s/ into /p/, but cleaning up a messy paradigm can bring it about in one go!

WotD: blackcurrant

1. die Johannisbeere
2. de aalbes, de zwarte bes
3. la grosella negra
4. la grosella negra
5. le cassis
6. y gyrren ddu
7. an cuirín dubh
8. 까치밥나무열매
9. 黑醋栗 hēicùlì

Notes: 8. Lit., "crow food tree fruit". 9. Lit., "black vinegar chestnut".