Definition of "jerkin"

[T]wenty yeomen, two and two, / In hosen black, and jerkins blue, / With falcons broider'd on each breast, / Attended on their lord's behest.

1808 February 22, Walter Scott, “Canto First. The Castle.”, in Marmion; a Tale of Flodden Field, Edinburgh: […] J[ames] Ballantyne and Co. for Archibald Constable and Company, […]; London: William Miller, and John Murray, stanza VIII, page 30

A tall and very good-looking kid in a jerkin came out of the store and rode the coupé off around the corner and came back walking, his glistening black hair plastered with rain.

1939, Raymond Chandler, The Big Sleep, Penguin, published 2011, page 32

I booked a room at the small hotel and deposited my luggage there. I bought myself strong boots, a pair of breeches, a jerkin, and a couple of shirts. Then I turned my back upon the town and climbed.

1952, Daphne Du Maurier, “Monte Verità”, in The Apple Tree