'Atreus' originates from Ancient Greek, specifically the name 'Ἀτρεὺς' (Atreus); the deeper linguistic origin is uncertain and may be pre-Greek or obscure in origin.

'Atreus' appears in Homeric and classical Greek as 'Ἀτρεὺς', was adopted into Latin as 'Atreus', and entered modern English usage through classical texts and translations referring to the mythological king.

Initially the term functioned solely as a proper name for the mythic figure; over time it also came to denote his descendants (e.g. 'Atreidae') and the tragic mythic associations of his house, but the core reference to the mythological person has remained.