Meaning

noun a manner of speaking that is natural to native speakers of a language

noun the usage or vocabulary that is characteristic of a specific group of people

noun the style of a particular artist or school or movement

originFrom Middle French idiome, and its source, Late Latin idioma, from Ancient Greek ἰδίωμα (idíōma, “a peculiarity, property, a peculiar phraseology, idiom”), from ἰδιοῦσθαι (idioûsthai, “to make one's own, appropriate to oneself”), from ἴδιος (ídios, “one's own, pertaining to oneself, private, personal, peculiar, separate”). By surface analysis, idi- + -om.

Etymology from Wiktionary, CC BY-SA 3.0