Where does the term "reservation price" come from (emphasis mine)?
"The term reservation price comes from auction markets. When someone wanted to sell something in an auction, he would typically state a minimum price at which he was willing to sell the good. If the best price offered was below this stated price, the seller reserved the right to purchase the item himself. This price became known as the seller's reservation price and eventually came to be used to describe the price at which someone was just willing to buy or sell some item.
That is from page 109 of Hal Varian's Intermediate Microeconomics book (3rd ed). Here are some links to Professor Varian's New York Times columns.