'synarthrotic' originates from Greek (via New Latin/medical Latin), specifically the elements 'syn-' and 'arthron', where 'syn-' meant 'together' and 'arthron' meant 'joint'.

'synarthrotic' developed from the medical New Latin noun 'synarthrosis' (from Greek 'synarthrosis'), and was adopted into English as the adjective 'synarthrotic' to describe things pertaining to a synarthrosis.

Initially related to the idea of 'joined together' or 'a joining of bones', the term evolved to refer specifically to an 'immovable joint' and things relating to such a joint.