'oversensitive' is a compound formed from the prefix 'over-' and the adjective 'sensitive'. 'Over-' originates from Old English 'ofer', where 'ofer' meant 'over, above, beyond' or 'too much'. 'Sensitive' originates ultimately from Latin, specifically the word 'sensitivus' (from 'sentire'), where 'sentire' meant 'to feel'.

'sensitive' came into English via Old French and Middle English from Latin 'sensitivus' (from 'sentire'). 'over-' has Old English roots as 'ofer' and was used in compounds to mean 'excessively' or 'beyond'. These elements combined in modern English to form the compound 'oversensitive'.

Originally, 'sensitive' meant 'capable of feeling or perceiving' (from Latin 'sentire'). Over time it came to mean 'easily affected or emotionally responsive'; with the prefix 'over-' the compound's meaning shifted to 'excessively or unduly sensitive' (i.e., 'too easily affected').