adulor.

The first component is evidently ad- (“to, toward”); the second one, however, has an obscure origin. It has been conjectured to come from an unattested *ūlos (“tail”), from Proto-Indo-European *h₂welh₁- (“hair; wool”), whence English wool (via Proto-Germanic) and velvet (via a Latin diminutive). Compare Lithuanian valai (“horsetail hair”) and Sanskrit वाल (vā́la, “tail of an animal; tail hair; fur”). The sense development might indicate a likening of such behavior to the wagging of a dog's tail, which is similarly deemed servile and submissive. Nevertheless, according to De Vaan (2008), those supposed cognates come from a Proto-Indo-European root that had no terminal i sound, which implies that it would not have yielded a Latin reflex with a long u in it (like adūlor). Alternatively, De Vaan (2007) connected it to avidus (“eager; avid”), through a root *adūlo-, from an earlier *adaulo, d-to-l dissimilation of *adaudo, from Proto-Italic *adawiþo (“eager toward [something or someone]”, adjective), so by surface analysis, ad + avidus, with meaning specialization: “eager toward someone” > “eager to get one's attention and favor” (to the point of fawning).