more on -nik

[Laurence Horn]

No, nudnik is not related to nudity.  I wanted to make sure what the actual
derivation was, although I suspected previous posters (relating it to
"noodge") were basically right.  Here's Ellen Prince, my expert on all
things Yiddish, on -nik:
====================
in slavic it's simply a nominalizing suffix -- makes a noun out of
anything, including a noun -- or so it seems without looking closely, of
course. but we do know sputnik and /tshaynik/ 'teapot', from /tshay/ 'tea'.
ok, in yiddish
it's always an *agent* -- so nudnik (from nudzhen 'annoy'), and a
ton of others less famous in english. now yinglish is clearly
influenced by yiddish (surprise, surprise) in beatnik, refusenik...

(the one exception in yiddish is in fact /tshaynik/ -- and the
standard explanation is that it was taken in toto, not made up in
yiddish of its parts.)