From older Latin iuvere (> iuvāre), apparently a simple thematic verb, to which iuvāre may originally be an iterative.
Maybe cognate with Hittite [Term?] (/iyauwatta/, “to be healed, recover”) (middle voice, meaning developed from "to help oneself"), in which case it is reconstructable as Proto-Indo-European *h₁i-h₁éwH-ti (“to help”), from root Proto-Indo-European *h₁ewH-.