If you've got your ducks in a row, you've got everything all lined up and ready to go. The expression comes from bowling, or ten pins. When the game moved from Europe to America, it was modified by introducing a short, slender pin that resembled a duck and so was called a duckpin. Those who reset pins were said to get their ducks in a row.
Where does the name for this North American duck come from? In the 17th century, it was the custom for courtiers to wear close-fitting jackets that covered them from their shoulders to their waist. They were made of leather. But for those who could not afford such finery, an less costly arrangement was made: Gallants had leather in the front and canvas in the back.
The "canvas back" doublets inspired the name for the common duck whose back feathers are white - unlike its front feathers.
Today, this reference to good shoes means that one is well-provided for in money and comfort. But originally, to be well-heeled meant that one carried a weapon.
The expression arose from the sport of cockfighting in the Middle Ages, in which a gamecock was equipped with a metal spur or gaff on the back of each foot. It was then placed in a cockpit where it was expected to fight an opponent to the death. A bird equipped in such a manner was called well-heeled, or armed for victory. (Cockfighting has been long outlawed in the United States and in many other countries.) While people never armed themselves in quite the same way, they did use firearms, which also made them "well-heeled."
In time, money became the equivalent of armor, and this well-used expression took on the narrower, but less dangerous, meaning of being financially prosperous.
SOURCES: 'The Encyclopedia of Word and Phrase Meanings,' by Robert Hendrickson; 'Brewer's Dictionary of Phrase and Fable,' by Ivor Evans; 'Why You Say It,' by Webb Garrison; 'Have A Nice Day!' by Christine Ammer.