Finnish word nainti comes from Finnish naida, Finnish -nti

Detailed word origin of nainti

Dictionary entry	Language	Definition
naida	Finnish (fin)	(transitive, + genitive-accusative) to marry.. (transitive, vulgar, + partitive) to have sex or sexual intercourse with somebody, copulate with somebody, fuck.
-nti	Finnish (fin)	Form action nouns from verbs whose first infinitive ends with a diphthong + -da/-dä.
nainti	Finnish (fin)	(vulgar) fucking. Marrying.

Words with the same origin as nainti