A spasm is a sudden constriction of a muscle or blood vessel. This idea can be generalized to anything that occurs suddenly and lasts a short while. Except for a brief spasm of yard work, you had a perfectly lazy Sunday.
The Greeks had a word called spasmós, which meant "to cramp or convulse." It also meant "to tear away or violently pull," which, if you've ever suffered a muscle spasm you know is a good definition. The word had a physical meaning up until around 1817, when it came to include the abstract. When you were invited to go hiking in the redwood forest, you could hardly control your spasms of joy. Make sure you stretch before hiking, so you don't get muscle spasms.