It's what all squires wear.
2 seconds sound clip from the The Sword in the Stone (1963) movie soundboard.
You can hear this line at 01:11:48.871 in the Blu-ray version of the movie.
Quote context
[...]
- Oh, Sir Ector! Oh... What. Whoa!
- Ha!
- Yes, indeed. A fine monkey suit for polishing boots.
- And I thought you were going to amount to something. I thought you had a few brains!
- A stooge for that big lunk, Kay.
- What do you want me to be? I'm nobody.
[...]