The origin of this word is unclear. Traditionally, it is explained as a borrowing from Belarusian dialectal за́йка (zájka), reshaped under the influence of kaķis (“cat”), but the similar Sudovian cognate makes this explanation dubious. It is difficult also to make it compatible with the Lithuanian and Slavic cognates. For the Slavic terms, there are various opinions, generally leading up to the Proto-Indo-European stem *ǵʰey- (“to drive, to exhort, to move quickly”). It is possible that the root of all those forms may be some pre-Indo-European word (*ǵa-, *ǵay-, *ǵuy-) to which Indo-European suffixes were attached. Cognates include Lithuanian dialectal zui̇̃kis, Sudovian zags, Old Church Slavonic заѩць (zajęcĭ), Russian, Belarusian за́яц (zájac), Ukrainian за́єць (zájecʹ), Czech zajíc, Polish zając.