"Stoic" is sometimes contrasted with "Epicure." If your beloved spouse tragically died young, leaving you with four kids to raise solo, you might very well be called "stoic" if you accepted your fate and soldiered on, rather than blubbering over it. Because that's what being stoic means — to accept whatever happens to you without complaining about it, and without showing emotion. Except, that's not quite right.
The original Stoic was someone who followed the teachings of Stoicism, a philosophical movement founded in Greece around 300 B.C.E. Popular during the Roman Empire, Stoicism was based on the concepts of meditation, mindfulness and self-examination, and offered practitioners theoretical precepts and inspirational texts to ponder. In essence, it was a bit like a religion, and has some striking similarities with Christianity [sources: Stanford Encyclopedia of Philosophy, Pigliucci].
So how did the word become linked with emotionless acceptance? Stoics spent a lot of time thinking about death and dying, often considered the ultimate test of one's character. And they did believe that emotions such as fear, envy or passionate love resulted from false judgments, and so a true Stoic would be immune to them. A virtuous life (and Stoics believed virtue was necessary for happiness) was a life that was free from passion [sources: Stanford Encyclopedia of Philosophy, Pigliucci].