I'm no linguist, but often I find myself fascinated by etymology. A phrase whose meaning has changed drastically that I often find myself pondering is "third world." At its beginning, the phrase described a country's political leanings rather than its economic status. All countries were given a label of first, second, or third world during the cold war. First world countries were the US and its allies. Second world nations were the USSR and its allies. Finally, third world countries were those which were unaffiliated. I find it strange how the term evolved, and so quickly.

What are some other words or phrases whose meanings have changed over time?