'antiasthenic' originates from the combining form 'anti-' (from Greek 'anti-' meaning 'against') and 'asthenic' (from Greek 'asthenēs' meaning 'without strength'), literally 'against weakness'.

'asthenic' comes from Greek 'asthenēs' (without strength) → Late Latin/Medieval usage 'asthenia'/'asthenes' → English 'asthenic'; 'anti-' (Greek) was later prefixed in Modern English formation to create 'antiasthenic'.

Initially formed to mean 'opposed to or counteracting weakness' in medical contexts, and it has retained this specialized meaning in modern usage.