'apsidiole' originates from French, specifically the word 'apsidiole', where 'apse' (from Latin 'apsis', Greek 'apsís') meant 'arch' or 'vault' and the diminutive suffix '-iole' meant 'small'.

'apsidiole' changed from Medieval/Old French and Medieval Latin forms such as 'apsidiola' (a diminutive of Latin 'apsis') and eventually entered modern English as 'apsidiole' via French.

Initially, it meant 'a small apse' (the diminutive sense of 'apse'), and this meaning has largely remained the same in modern usage.