'resize' is a modern English formation from the prefix 're-' (from Latin 're-' meaning 'again' or 'back') + the noun 'size' (English), meaning 'measure or dimension'.

'size' came into Middle English from Old French (e.g. 'size' or related forms) referring to an assigned amount or measurement; English speakers formed 'resize' by adding the productive prefix 're-' to 'size', and 'resizing' developed as the -ing form.

The formation originally meant 'set or adjust size again'; over time it has come to be used broadly for 'change the size' (either increase or decrease) in general and technical contexts.