'apse-related' originates from modern English compounding of 'apse' + 'related'. 'apse' ultimately derives from Latin 'apsis' (from Greek 'ἁψίς' / 'hapsis'), where 'apsis' meant 'arch' or 'vault'. 'related' comes from Latin 'relatus', the past participle of 'referre' (re- + ferre), via Old French and Middle English.

'apse' passed from Greek 'ἁψίς' to Latin 'apsis', appeared in Medieval Latin and Old French, and entered Middle English as 'apse'. 'relate' developed from Latin 'referre' → Medieval/Old French forms → English 'relate', with 'related' as the adjectival/past participle form; the compound 'apse-related' is a modern English formation combining these elements.

Initially 'apsis' referred to an arch, vault, or recess; over time English 'apse' came to denote the semicircular or polygonal recess of a church. 'Related' maintained the sense 'connected to'. Together as 'apse-related' the compound specifically denotes 'connected with an apse'.