Definition of "spinage"

Take a quart of good boiling pease which put into a pot with a gallon of soft water whilst cold; add thereto a little beef or mutton, a little hung beef or bacon, and two or three large onions; boil all together while your soop is thick; salt it to your taste, and thicken it with a little wheat-flour; strain it thro' a cullender, boil a little sellery, cut it in small pieces, with a little crisp bread, and crisp a little spinage, as you would do parsley, then put it in a dish, and serve it up.

1764, Elizabeth Moxon, English Housewifery Exemplified‎