haver grass
/ˈheɪvə ˌɡras/ /ˈheɪvə ˌɡrɑːs/Chiefly English regional (northern ) and Scottish. Now rare
noun
Any of various grasses related to the cultivated oat (Avena sativa) or thought to resemble it.
Origin
Late 16th century; earliest use found in Henry Lyte (1529–1607), botanist and antiquary. From haver + grass.