It should come as no surprise that the Romans dedicated a month to their most belligerent deity, Mars. Wars and conquests were a large part of Roman life - and March marked when it was warm enough to resume fighting.
March also had the distinction of being the first month of the Roman year. Starting with March made sense, for it came after what the ancients called "the dead of the year," or winter. In March, signs of growth begin to appear. But after the adoption of the Julian calendar in 46 BC, March was bumped from first-month status.
Through the years, March's trademark blustery winds and changeable weather have earned it several terms and expressions. There is an old saying we still hear that March "comes in like a lion and goes out like a lamb."
The expression may have been inspired by poet William Dean Howells who wrote: "Tossing his mane of snows in wildest eddies .../ Lion-like March cometh in hoarse...."
And in Britain, people recognized March's calmer weather at the end of the month. An old saying had it that March borrowed three days from April. So the last three days of March were often called the "borrowed days."
SOURCES: 'All About the Months,' by Maymie R. Krythe; 'Why You Say It,' by Webb Garrison; 'A Second Browser's Dictionary,' by John Ciardi; 'Brewer's Dictionary of Phrase and Fable,' by Ivor Evans; 'Room's Dictionary of Changes in Meaning,' by Adrian Room; 'Dictionary of Word Origins,' by Joseph Shipley; 'Barnhart Dictionary of Etymology,' by Robert Barnhart.