'Western-themed' is a compound formed in modern English from 'western' + 'theme'. 'Western' originates from Old English 'west' (direction 'west') with the adjectival suffix '-ern'. 'Theme' originates from Greek 'thema' via Latin and Old French, where 'thema' meant 'that which is placed' or 'subject'.

'Western' comes from Old English 'west' and developed through Middle English into the modern adjective 'western'; 'theme' entered English from Latin/Old French (from Greek 'thema') and came to mean 'subject' or 'motif'. The compound 'Western-themed' arose in modern English by combining the adjective 'western' with the noun 'theme' (with a past-participial form 'themed' used attributively).

Individually, 'western' originally meant 'to the west' and 'theme' meant 'subject' or 'that which is set'; together in modern usage they now mean 'having a theme based on the Western (especially Old West) motif.'