'disinfectant' originates from French 'désinfectant', ultimately built from the prefix 'dis-' (meaning 'do the opposite of') plus the verb 'disinfect' (itself from Latin components related to 'inficere'/'infect-'), where the element 'infect' relates to Latin roots meaning 'to taint' or 'to infect'.

'disinfectant' entered English in the mid-19th century from French 'désinfectant', formed from the verb 'désinfecter' (French) and ultimately tracing back to Latin elements (e.g. 'inficere'/'infect-'); the English noun developed by adding the agentive suffix '-ant' to the verb 'disinfect'.

Initially and historically it referred to an agent that removes or prevents infection/contamination; this core sense has remained largely stable into modern usage as 'a substance that disinfects.'