'asthenophobia' originates from Greek, specifically the elements 'asthenēs' and 'phobos', where 'asthenēs' meant 'weak' and 'phobos' meant 'fear'.

'asthenophobia' was formed in modern English by combining the Greek-derived combining form 'astheno-' (from Greek 'asthenēs' via New Latin 'asthenia') with the Greek-derived suffix '-phobia' (from Greek 'phobos'), resulting in the modern medical/colloquial term 'asthenophobia'.

Initially, the roots referred to 'weakness' and 'fear' separately; over time the compound came to mean specifically an irrational fear of fainting or weakness, a usage consistent with modern medical/psychological terminology.