'antipruriginous' is formed from the prefix 'anti-' (from Greek 'anti-' meaning 'against') combined with 'pruriginous' (relating to 'pruritus', Latin 'pruritus' meaning 'itch').

'pruritus' (Latin) gave rise to Late Latin/Medieval forms like 'prurigo' and adjective 'pruriginosus'; English adopted 'pruritic'/'pruriginous' for 'relating to itching', and the modern English adjective 'antipruriginous' was formed by adding the prefix 'anti-' to denote action against itching.

Originally the Latin root referred simply to 'itching' ('pruritus'); over time compounds with 'anti-' came to denote agents or qualities that relieve or prevent itching, which is the current meaning of 'antipruriginous'.