'theologize' originates from Modern English, specifically formed from the noun 'theology' + the verb-forming suffix '-ize', where 'theology' ultimately comes from Greek 'theologia' and 'theo-' meant 'god' and 'logia' meant 'speech' or 'study'.

'theologize' developed in English by attaching '-ize' to 'theology' (itself from Greek 'theologia' via Latin and Old French forms). Middle English had forms of 'theology' (e.g. 'theologie'), and the verb form emerged later in Early Modern to Modern English as 'theologize' (with an alternate British spelling 'theologise').

Initially related simply to 'speaking or writing about God' (as in 'theologia'), it evolved into the specific verbal sense 'to engage in theological argument or speculation' used in modern English.