'inhomogeneity' originates from Latin and Greek, specifically from the Latin prefix 'in-' (meaning 'not') combined with Greek 'homogenēs' (via Latin/Modern Latin 'homogenitas'), where 'hom(o)-' meant 'same' and 'gen(os/ēs)' meant 'kind' or 'type'.

'inhomogeneity' was formed in Modern English by prefixing Latin 'in-' to the existing word 'homogeneity' (which itself came into English via Latin/Modern Latin from Greek 'homogenēs'); over time the compound became the standard English noun 'inhomogeneity'.

Initially it simply denoted 'not homogeneous' or 'not of the same kind throughout'; over time its use broadened and became established in technical fields (materials science, physics, statistics, cosmology) to describe specific kinds of internal variation or irregularity.