On this side of the pond dungarees are the same thing as overalls and not the same as jeans. The word is quite old.

Dungarees: plural noun; British, American and Australian overalls - a pair of trousers that has an extra piece of cloth that covers the chest and is held in place by a strap over each shoulder.

(American) Dungarees are also clothes, esp. trousers and coats, made of denim.

1613, from Hindi dungri "coarse calico."