Green’s Dictionary of Slang

schnicky-schnacky n.

[redup. of schnack n.]

(US campus) physical affection in public.

[US]Eble Sl. and Sociability 42: Vowel alternation is heard in schnicky-schnacky ‘public display of affection’. [Ibid.] 78: Schnack and schnicky-schnacky ‘affection’ sound like mock Yiddish.