'reward-insensitive' originates from modern English, formed by combining the noun 'reward' and the adjective 'insensitive' (itself from the negative prefix 'in-' + 'sensitive'). Here 'reward' originally denotes something given in return as an incentive or payment, and the prefix 'in-' means 'not', while 'sensitive' means 'capable of responding or being affected'.

The components evolved separately: 'reward' comes from Middle English (from Old North French/Anglo-Norman roots meaning regard/protection and later 'return' or 'payment'), while 'insensitive' derives from Latin 'sensitivus' (from 'sentire', 'to feel') via French/Latin forms; the compound 'reward-insensitive' is a relatively recent English coinage combining these elements to describe lack of responsiveness to rewards.

Individually, 'reward' historically referred to regard or recompense and 'insensitive' to lack of sensory/feeling; together the compound came to mean specifically 'not affected by reward signals'—a more technical, behavioral or psychological sense than the separate words had on their own.