'methoxy-substituted' is a compound formed from 'methoxy' + 'substituted'. 'Methoxy' is a chemical combining form derived from 'methyl' (coined in the 19th century in organic chemistry) plus the combining form '-oxy' (from Greek 'oxys', used to indicate oxygen-containing groups). 'Substituted' comes from Latin 'substituere' meaning 'to put in place of'.

'methoxy' arose in 19th-century chemical nomenclature from 'methyl' + '-oxy'; 'substituted' entered English via Latin 'substituere' through Old French and Middle English as forms of 'substitute', and the past-participle adjective 'substituted' was established in scientific usage. The compound adjective 'methoxy-substituted' developed in chemical literature to describe derivatives bearing methoxy groups.

The original elements referred separately to a methyl-derived oxygen group and the action 'to place in the place of'; combined in modern chemistry the term now specifically denotes that one or more methoxy groups replace hydrogen(s) on a parent molecule.