pusillus.

Proto-Italic *put-sle-los → *pussillos followed by degemination via the so-called "mamilla rule", from Proto-Indo-European *put-lo- (“son”), historically standing in relation to pullus (“young of an animal”) as a diminutive. Latin cognates include pusillus, putillus (“tiny”), pūsus (“boy”), possibly Vulgar Latin *pūtta (“whore”). Further cognate to Faliscan putellio (“little son”, nom.sg.), Oscan puklum (acc.sg.), Paelignian puclois (dat.pl.), Sanskrit पुत्र (putrá, “son, child”), Avestan 𐬞𐬎𐬚𐬭𐬀 (puθra, “child, son”), Lithuanian putýtis (“little bird”), Latvian putns (“bird”), Old Church Slavonic пътица (pŭtica, “bird”). For the correspondence pullus :: pusillus compare paullus :: pauxillus, vēlum :: vēxillum. Compare pisinnus, pitinnus; see also putus, a ghost word. A connection of the stem *put- with puer is difficult to establish.