'demasculinize' originates from Latin and Greek-derived elements: from Latin prefix 'de-' (meaning 'remove' or 'reverse'), from Latin 'masculus' (meaning 'male'), and the suffix '-ize' (via Greek '-izein') meaning 'to make or cause to be'.

'demasculinize' was formed in modern English by attaching the prefix 'de-' to 'masculinize'. 'Masculinize' derives from French 'masculiniser' and ultimately from Latin 'masculinus' (from 'masculus'), which meant 'male' or 'manly'. The combination produced the modern English 'demasculinize'.

The root 'masculine' originally meant 'male' or 'manly'; 'masculinize' meant 'to make masculine'. With the prefix 'de-' the composite came to mean 'to remove or reduce masculinity', which is its current meaning.