'arcadian' originates from Greek, specifically the word 'Ἀρκαδία' (Arkadía), where the name referred to the region Arcadia in Greece.

'arcadian' changed from the Greek place-name 'Ἀρκαδία' into Latin 'Arcadia' and Medieval/Modern Latin uses, then entered English via literary and classical references (through Renaissance and later), becoming the English adjective and noun 'arcadian'/'Arcadian'.

Initially, it meant 'from Arcadia' (a geographic origin), but over time it evolved into the figurative sense 'idyllically rural or pastoral', influenced by classical and pastoral literature.