in numerals is the initial of mille, a thousand.
“Whosoever prayeth for the soul of John Gower he shall, so oft as he so doth, have a M and a D days of pardon.”—Gower’s Tablet.
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Entry taken from Dictionary of Phrase and Fable, edited by the Rev. E. Cobham Brewer, LL.D. and revised in 1895.
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