noundialect Scottish, British
Any of various kinds of wild vetch, especially bitter vetch, Lathyrus linifolius, and tufted vetch, Vicia cracca. Also: the fruit of such a vetch.
Old English; earliest use found in Antwerp Glossary. From mouse (or occasionally its plural mice) + pease; in later use in some forms the second element was probably apprehended as plural.