'ankylosed' ultimately originates from Greek via New Latin/medical formation; specifically from the Greek root 'ankyl-' (Ancient Greek 'ἄγκυλος' / 'ankylos'), where 'ankyl-' meant 'bent, hooked, crooked'.

'ankylosed' developed through the medical noun 'ankylosis' (from Greek 'ankylōsis') into the Verb/Noun pair in Late Latin/New Latin and then into English as the verb 'ankylose' and its adjective/past participle 'ankylosed'.

Initially related to the idea of 'bent' or 'hooked'; over time it became a technical medical term for the pathological stiffening or fusion of a joint, and the modern adjective/verb sense denotes having become fused or immobile.