'reabsorb' originates from Latin components: the prefix 're-' (from Latin 're-') and the verb 'absorbere' (Latin), where 're-' meant 'again' and 'absorbere' meant 'to suck in' (from 'ad-' + 'sorbere').

'absorbere' in Latin (literally 'to suck in') passed into Old French as 'absorber' and into Middle English as 'absorb'; the prefix 're-' (Latin) was later added to form the compound 'reabsorb' in modern English.

Initially it meant 'to suck in' (the sense carried by Latin 'absorbere'); over time the compounded form 'reabsorb' developed the more specific meaning 'to absorb again' or 'to take back into' in medical and technical contexts.