Avian origin of 'pie'
Four and 20 blackbirds may have been baked in a pie in that famous nursery rhyme, but the origin of the word "pie" has to do with another bird - the magpie. In the Middle Ages, this chatty flyer was referred to as "pie," from its Latin name, pica. The pie had a habit of stealing small objects, like string, pebbles, and glass, and lining its nest with them. Cooks were also collectors; they could not afford to be wasteful. At some point, an inspired homemaker put leftover vegetables and meat in a pastry shell. The filling resembled the magpie's clutter, and so, the penny-saving concoction became known for the thieving bird.
Similarly, printers use the term "pi" for any words that are badly printed and look jumbled - like a pie or a magpie's nest.
And anything printed in black letter type on white paper was said to give a "pied" appearance, again from the magpie whose plumage is black and white. Even the Pied Piper is varicolored, and a horse spotted in two or more colors is "piebald."
Hop inside the stove
Can you imagine sitting inside a stove instead of beside it? That's what you might have done 800 years ago. The word comes from old English "stofa": A heated room used for sweating and introduced to the English by the Scandinavians. Stofa changed its spelling to stove in the 15th century, 100 years before its meaning went from a steam bath to any device that throws off heat. In some places today, greenhouses and pottery kilns are still called stoves.
Anyone who has cut into an onion knows that it has many layers. And they all fit tightly together. Onion derives from the Latin unus meaning "oneness." It's the same root that gives us unit, unity, union, and unison. The meaning of a group of people or states united for a purpose was first recorded in 1660, followed by "labor union" in 1833.
SOURCES: 'A Browser's Dictionary,' by John Ciardi; 'The Encyclopedia of Word and Phrase Origins,' by Robert Hendrickson; 'The Barnhart Dictionary of Etymology,' by Robert Barnhart; 'Why You Say It,' by Webb Garrison; 'Eat Your Words,' by Charlotte Foltz; 'Dictionary of Word Origins,' by Joseph Shipley; 'Brewer's Dictionary of Prose and Fable,' edited by Ivor Evans; 'Morris Dictionary of Word and Phrase Origins,' by William Morris; The World Book Dictionary; The Oxford English Dictionary; Webster's Dictionary.