'non-condensing' originates from Modern English, specifically formed from the prefix 'non-' meaning 'not' and the present participle 'condensing' from the verb 'condense'.

'condense' derives from Latin 'condensare' (to make dense), from 'con-' (together) + 'densus' (thick); it passed into Middle English via Late Latin/Old French (e.g. medieval forms like 'condensen') and became modern English 'condense', with 'non-' later attached to form 'non-condensing'.

Initially 'condense' meant 'to make dense' or 'to compress'; over time it came to be used especially for the phase change from gas to liquid, and 'non-condensing' now means 'not undergoing that phase change' (not forming liquid).