From Proto-Indo-European *ǵen-, *ǵnō-, *ǵneh₃- (“to know, to recognize”) (whence also zināt, q.v.), possibly of the same origin as *ǵenh₁- (“to create, to generate”) (> “to give birth”, “to have/be a relative”). The initial meaning of znots was apparently “(new) relative”, “man who married into the family/clan”, from which it was restricted to “son-in-law” (note that an 18th-century source still had it as “brother-in-law”). Cognates include Lithuanian žéntas (“son-in-law”), Proto-Slavic *zętь (Old Church Slavonic зѧть (zętĭ), Russian зять (zjatʹ), Belarusian зяць (zjacʹ), Bulgarian зет (zet), Czech zeť, Polish zięć), Sanskrit ज्ञाति (jñatí, “relative”), Ancient Greek γνωστός (gnōstós, “blood relative, brother”).