'legendize' originates from the English noun 'legend' (from Latin 'legenda', literally 'things to be read') combined with the productive verbal suffix '-ize' (from Greek '-izein' via Late Latin/Old French), where 'legend' referred to a narrative or account and '-ize' meant 'to make' or 'to render'.

'legend' comes from Latin 'legenda' > Old French 'legende' > Middle English 'legend'. The verbal formation using '-ize' is a modern English productive process (from Greek/Latin/French), producing 'legendize' in modern English to mean 'to make into a legend' or related senses.

Initially, 'legend' meant 'things to be read' or 'a narrative' and later came to mean a traditional or popular story often about heroes; over time the derived verb 'legendize' developed to mean 'to turn into a legend' (and by extension in technical contexts 'to add a legend/caption').