'inpatient' originates from Modern English as a compound of the prefix 'in-' and the noun 'patient'; 'patient' itself comes from Old French 'patient' (from Latin 'patiēns'/'patiēnt-') where the Latin root 'pati-' (from 'patior') meant 'to suffer, endure'.

'patient' passed from Latin 'patiēns' into Old French as 'patient' and then into Middle/Modern English as 'patient'; the element 'in-' (meaning 'in' or 'within', ultimately from Latin 'in-') was later combined with 'patient' in Modern English to form 'inpatient' with the medical sense of someone admitted to hospital.

Initially, the root conveyed the idea 'to suffer or endure'; over time 'patient' came to mean 'a person receiving medical care', and the compound 'inpatient' evolved to specify a person receiving care while admitted to a hospital.