I lived in Carlisle for a while and was surprised to see carlins on sale. The only place I'd ever seen them before was in the Black Country where I was brought up (Darlaston), where they were called grey peas (pronounced 'gray pays') and eaten all year round, usually with a cheap ham hock to add extra flavour.
Dry and uncooked they made excellent ammunition for our 'pea shooters', too.
The green ones were called (in our house, at least) blue pays . . . . I have no idea why!