'informant' originates from Latin, specifically the word 'informare', where 'in-' meant 'into' and 'formare' meant 'to form or shape'; the agentive suffix '-ant' comes from Latin '-antem' used to form nouns meaning 'one who ...'.

'informant' developed via Middle English (from verbs such as 'inform' from Old French/Latin influence) with the agent noun formed by the suffix '-ant', and eventually became the modern English noun 'informant'.

Initially related to 'forming' or 'giving shape' (through 'informare'), its meaning shifted to 'one who imparts knowledge or information', and later specialized to both 'a source of information for authorities' and 'a person who provides data to researchers'.