'Aquinas' originates from Medieval Latin, specifically the byname 'Aquinas', where it meant 'of Aquino' (indicating origin from the town Aquino in Italy).

'Aquinas' developed from the Latin locational byname 'de Aquino' (literally 'of Aquino') used to identify Thomas de Aquino; over time the form 'Aquinas' became established as a surname and as the conventional reference to Thomas himself.

Initially it meant 'from Aquino' (a place-name indicator). Over time it evolved into a family name and then into a conventional proper name referring especially to Thomas Aquinas and, by extension, to his philosophical school (Thomism).