'antimony-free' is a modern English compound formed from the noun 'antimony' and the adjective/suffix 'free', where 'antimony' comes via Old French 'antimoine' and Medieval Latin 'antimonium' referring to the element, and 'free' comes from Old English 'freo' meaning 'not in the power of' or 'without'.

'antimony' changed from Medieval Latin 'antimonium' and Old French 'antimoine' into the modern English word 'antimony'; 'free' changed from Old English 'freo' to modern 'free'. The compound 'antimony-free' arose in modern English (chiefly in scientific/technical contexts) to denote absence of the element.

Initially, 'free' meant 'not under the control of' and over time it has been used in compounds to mean 'without' (as in 'sugar-free'); thus 'antimony-free' now means 'without antimony'.