'Avalon' originates from Old Welsh (Brythonic), specifically the word 'Avallach' or 'Avallon', where 'avall' meant 'apple' (so roughly 'isle of apples').

'Avalon' appears in medieval Latin and French writings (e.g. Geoffrey of Monmouth's Latinized forms such as 'Avalonem' in the 12th century) derived from Old Welsh 'Avallach'; over time it entered Middle English and then modern English as 'Avalon'.

Initially, the name meant 'island of apples' (a literal botanical or place-name sense), but over time it took on a mythic/otherworldly sense as an enchanted, paradisiacal isle associated with King Arthur.