Abastante is a rare Italian surname, not documented as an autonomous entry in the classic onomastic repertories consulted. The most likely etymology derives it from the present participle of the old Italian verb abastare or abbastare (to suffice, to be enough, from Late Latin abbatare, derived from basta, a word of Germanic or Greek origin linked to the concept of limit or sufficiency), applied as an affectionate or descriptive nickname to an ancestor characterised by his moderation, his capacity for self-reliance or his economic self-sufficiency.

Under this reading, Abastante would literally mean "the one who suffices" or "the one who has enough", with the positive sense of a moderate person content with what is necessary. An alternative hypothesis links it to the Italian adjective abundante or abbondante (abundant, prosperous, from Latin abundans), with dialectal apocope of the intervocalic d, applied as an auspicious-economic nickname to a newborn so that he would have material abundance. The form Abastante is a minority one compared with the better-documented variant Bastante or Abbastante. It belongs to the broad onomastic group of Italian surnames derived from modal verbs and participles, alongside Basta, Basto and Bastoni. The surname's distribution is very limited. As it does not appear as an autonomous entry in the classic Italian onomastic repertories consulted, the proposed etymology should be regarded as indicative.