Once, in his first term, Cartwright had been bold enough to ask him why he was so clever, […] ‘It’s memory, Cartwright, old dear. Memory, the mother of the Muses . . . at least that’s what thingummy said.’ ‘Who?’ ‘You know, what’s his name, Greek poet chap. Wrote the Theogony . . . what was he called? Begins with an “H”.’ ‘Homer?’ ‘No, dear. Not Homer, the other one. No, it’s gone. Anyway. Memory, that’s the key.’
Source: wiktionary