coniveo.

Disputed. According to De Vaan, from earlier Proto-Italic *kom-kneiɣʷēō, from *kom- + *kneiɣʷēō, perhaps from Proto-Indo-European *kneygʷʰ- (“to bend, to droop”). Rix suggests that the term derives from a Proto-Indo-European causative formed from *kneygʷʰ- + *-éyeti. According to Sihler, the possible Proto-Italic causative form *kom-knoyɣwejō may have undergone a phonological development from *kom-knoyɣwejō to *kongneyw- before culminating in connīveō. Sihler suggests that connīveō is the earlier form and that cōn- originates from connīveō via a possible Latin sound change in which long nasal consonants were shortened when placed after a short vowel followed by compensatory lengthening of the prior short vowel. Sihler suggests that this same sound shift may have occurred in Latin āmentum, perhaps from ammentum. However, a causative form *knoyʷʰéyeti would produce a Proto-Italic term beginning with *knoi-, and De Vaan suggests that the long vowel ī in -nīveō indicates a Proto-Italic diphthong *-ei-. Instead, De Vaan suggests that the term could derive from a Proto-Indo-European stative. According to De Vaan, the term shows a more specific phonetic development of *komkn-, to *koŋɣn-, to *koɣn-, before culminating in cōn-. De Vaan considers it possible that the term, and its Germanic cognates, actually derive from a substrate language due to unusual root structure and the limited distribution of Indo-European cognates. Cognate with nicō, nictō, nītor (“to bear or rest upon something”), and with Proto-Germanic *hnīwaną.