Mashlum is a Scottish expression for a mixture made with a mixture of flours, rather than entirely from one grain, such as oatmeal, barley or wheat.
In English, we’d just say “mixed grain.”
Literature & Lore
“Tell you guid bluid o’ auld Boconnock’s
I’ll be his debt twa mashlum bonnocks…”
— Robert Burns. “The Author’s Earnest Cry and Prayer”. 1786.