'ankylosis' originates from New Latin/Greek, specifically from Greek 'ankylōsis' (ἀγκύλωσις), where the root 'ankyl-' meant 'bent, crooked, or fused' and the suffix '-osis' indicated a medical condition.

'ankylosis' changed from Greek 'ankylōsis' into Late Latin/New Latin medical usage 'ankylose/ankylosis' and eventually entered modern English as 'ankylosis' (with related verb 'ankylose').

Initially it referred to a bending or crookedness (from Greek), but over time it evolved into the medical sense of 'abnormal stiffening and immobility of a joint due to fusion'.