'hyperreactively' originates from Greek, specifically the prefix 'hyper-' where 'hyper-' meant 'over' or 'beyond', combined with the English word 'reactive' (from 'react') and the adverbial suffix '-ly'.

'react' comes from Latin elements 're-' + 'agere' ('to do, drive'), developed into Old French (réagir) and then English 'react'; the adjective 'reactive' formed in English with the suffix '-ive'; in Modern English the prefix 'hyper-' (Greek) was attached to form 'hyperreactive', and the adverbial form 'hyperreactively' was formed by adding '-ly'.

Initially the parts meant 'over/beyond' (hyper-) and 'to act' (from Latin 'agere'); over time they combined in English to convey an excessive or exaggerated responsiveness, and the adverb now means 'in an excessively responsive manner.'