Ships' prisons (5)

I believe the answer is:

brigs

I'm a little stuck... Click here to teach me more about this clue!

'ships' prisons' is the definition.
The definition and answer can be both man-made objects as well as being plural nouns.
Perhaps there's an association between them I don't understand?

This is all the clue.

Can you help me to learn more?

(Other definitions for brigs that I've seen before include "vessels" , "jugs?" .)

I've seen this clue in The Globe and Mail.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.