nitor.

Disputed. * De Vaan suggests that, based on the form nīxus, it is likely that the original root ended with a velar. According to De Vaan, it may be connected with the root Proto-Indo-European *kneygʷʰ- (“to bend, to droop”), whence also possibly Latin connīveō. If the term is related to connīveō, then gnixus—a supposedly archaic form mentioned by Festus—may genuinely reflect an archaic stage of the Latin term. If this possibility is accepted, then the older form of nītor may have been *gnītor. * Possibly a back-formation from nīsus, although De Vaan considers there to be no other sufficient model for such a development. * Rix connects the term with Sanskrit यतते (yatate), itself from the root यत् (yat). According to this theory, the term could derive from the prefix *ní- combined with a thematic present from Proto-Indo-European *yet-. De Vaan rejects this comparison, arguing that the unclear nature of the original meaning of the Latin term prevents a definitive connection with the Sanskrit term. Moreover, De Vaan notes that *ní is never used as a prefix in Latin. * The linguist Andrey Shatskov connects the term with terms such as Lithuanian ap-ni̇̀kti, Old Church Slavonic никнѫти (niknǫti), and Ancient Greek νεῖκος (neîkos). Shatskov reconstructs a root *neyk- (“to approach energetically”). Shatskov argues that the archaic forms mentioned by Festus are intentionally archaicizing and likely formed according to the model of terms such as nōscō and gnōscō.

Etymology tree Latin niteō Proto-Indo-European *-os Proto-Indo-European *-s Proto-Indo-European *-ōs Proto-Italic *-ōs Latin -or Latin nitor From niteō (“to shine”) + -or.