'dogmatize' originates from Modern English formation: the adjective 'dogmatic' + the verb-forming suffix '-ize'; 'dogmatic' ultimately comes from Greek 'dogmatikos' via Latin and French, where Greek 'dógma' meant 'opinion' or 'that which is thought'.

'dogmatize' was formed in English by attaching '-ize' to 'dogmatic' (from Medieval/Modern Latin and Old French forms of Greek 'dógma'); Greek 'dógma' passed into Latin as 'dogma', then into Old French/Medieval Latin as forms meaning 'opinion' or 'decree', then into English as 'dogmatic' and finally 'dogmatize'.

Originally related to 'dogma' meaning an opinion or decree, the verb developed the specific sense 'to assert opinions (often arrogantly) as if they are unquestionable', a nuance that became the primary modern meaning.