'untestable' originates from the prefix 'un-' meaning 'not' and the word 'testable', which comes from the Latin 'testari', meaning 'to witness'.

'testari' transformed into the Old French word 'test', and eventually became the modern English word 'test' through Middle English.

Initially, 'test' meant 'to witness or affirm', but over time it evolved into its current meaning of 'to examine or evaluate'.