pern v.

"to move with a winding motion," a word used in poetry by Yeats from c. 1920, probably from a variant of dialectal pirn (n.) "small cylinder on which thread or yarn is wound (mid-15c.), which seems to have survived in dialects in Celtic parts of Britain. It is perhaps from prin "a twig, shoot of a tree" (c.1400), itself a variant of prene "a nail, spike," from Old English preon.