Origin of a phrase

Where did "an apple a day keeps the doctor away" originate from

I don't know its origin, but it's very old. There's clearly a strong element of rhyming slang in the derevation. Perhaps it has something to do with the scurvey (vitamin C deficiency) experienced by many 18thC sailors. An apple would be a fine source of this vitamin, as are limes - hence 'limey' for Brits, because their ships used to carry this fruit to ward off scurvey.