'character-themed' originates in Modern English as a compound of 'character' and the past-participle adjective-form 'themed' (from 'theme'). 'character' comes via Latin and Old French from Greek 'kharaktēr', and 'theme' comes from Greek 'thema' via Latin.

'character' passed from Greek 'kharaktēr' into Late Latin and Old French and then Middle English as 'caracter' before becoming Modern English 'character'. 'theme' comes from Greek 'thema' -> Latin 'thema' -> adopted into English; the adjective 'themed' is formed in Modern English from 'theme' + '-ed'. The compound 'character-themed' is a recent Modern English formation combining those elements.

Originally, 'character' meant a 'mark or distinctive sign' (from Greek), and later came to mean a 'person in a play or story' — the sense used in 'character-themed'. 'theme' originally meant 'something laid down' or 'a subject' and evolved to mean 'topic or motif'; combined, the compound now means 'based on a character as the motif.'