You're actually thinking of the Andromeda Galaxy, not constellation. It's not a constellation, but rather a whole other galaxy!

Here's why it's called Andromeda:

* Greek Mythology: The galaxy is named after the Greek mythological princess Andromeda, who was chained to a rock as a sacrifice to a sea monster. The hero Perseus rescued her, and they lived happily ever after.

* Location: The galaxy appears in the night sky near the constellation Andromeda, which itself is named after the princess. This proximity gave the galaxy its name.

So, while the galaxy is named after the constellation, the constellation itself is named after the mythical princess. It's a bit of a double-naming situation!