From Wiktionary, the free dictionary
From Old French plain, from Latin plēnus, from Proto-Indo-European *pl̥h₁nós (“full”).
plloin m
- (Guernsey) full
1903, Edgar MacCulloch, “Proverbs, Weather Sayings, etc.”, in Guernsey Folk Lore[1], page 532:Caud Mai, gras chimequière, fred Mai, granges pllaïnes.- A warm May, a fat churchyard, a cold May, full granaries.