'phobic' originates from Greek, specifically the word 'phobos', where 'phobos' meant 'fear'; the adjective was formed in English by combining 'phobia' with the suffix '-ic' (from Greek '-ikos').

'phobic' developed in English in the late 19th century from 'phobia' (itself from Greek 'phobos') plus the adjectival suffix '-ic' derived via Latin/Greek '-ikos', producing the modern English form 'phobic'.

Initially it meant 'relating to or caused by a phobia', and over time it has come to be used both as 'having an irrational fear' and as a noun meaning 'a person with a phobia'.