'synaptic' originates from Greek via New Latin, specifically from the Greek word 'synapsis', where 'syn-' meant 'together' and 'haptein' (root) meant 'to fasten' or 'to join'. The English adjective was formed by adding the suffix '-ic' to 'synapse'.

'synaptic' changed from the Greek word 'synapsis' to the New Latin/Modern scientific term 'synapsis' and the related noun 'synapse' in English; the adjective form 'synaptic' was later formed in scientific usage (19th–20th century) to describe things pertaining to synapses.

Initially it referred to a 'joining together' (general sense), but over time it evolved to the current specialized meaning 'relating to the junction between nerve cells (synapses)'.