'angelologist' originates from Greek, specifically the word 'angelos', where 'angelos' meant 'messenger' (later 'angel'), combined with Greek 'logos' meaning 'study' (through the suffix '-logy') and the agentive suffix '-ist' from modern English/Latin.

'angelos' passed into Late Latin as 'angelus', then into Old English as 'engel' and Middle English as 'engel/angel', giving modern English 'angel'; 'angel' combined with the suffix '-ology' (from Greek 'logos') formed 'angelology', and the agentive suffix '-ist' produced 'angelologist'.

Initially 'angelos' meant 'messenger' (a spiritual being); over time the components were combined into a technical term whose modern meaning is 'one who studies angels'.