'apse' originates from Greek, specifically the word 'apsis', where 'apsis' meant 'arch' or 'vault'.

'apse' changed from Greek 'apsis' to Latin 'apsis', passed into Old French as 'apse', and eventually became the modern English word 'apse' through Middle English.

Initially, it meant 'arch' or 'arch-shaped structure', but over time it evolved into its current meaning of 'a semicircular or polygonal recess at the end of a church'.