'astrologous' originates from Greek via Late Latin, specifically from Medieval Latin 'astrologicus' and Latin 'astrologus', where Greek 'astron' meant 'star' and 'logos' meant 'study' or 'discourse'.

'astrologous' evolved from Medieval Latin 'astrologicus' (adjective relating to astrology) and Late Latin 'astrologus' (astrologer), passing into English by analogy with other -ous adjectives like 'religious' or 'dangerous'.

Initially it meant 'relating to astrology or an astrologer', and over time it has retained that core sense though it is rare and often replaced by 'astrological'.