'non-transposing' is formed from the prefix 'non-' (from Latin 'non', meaning 'not') + the present participle of 'transpose' (from Latin 'transponere').

'transpose' originates from Latin 'transponere' (trans- 'across' + ponere 'to place'), passed into Old French as 'transposer' and Middle English as 'transposen' before becoming modern English 'transpose'; the prefixed form 'non-transposing' is a modern compound formed by adding 'non-' to the participle.

Initially, Latin 'transponere' meant 'to place across' or 'to transfer'; over time 'transpose' developed the sense 'to change order' and, in music, 'to change key.' 'Non-transposing' therefore came to mean 'not changing key or order' and is now used especially to indicate instruments or parts that sound at written pitch.