Possibly ᄂᆞᄌᆞᆨ (nocok, “being low”) + 아ᇦ (-aW-, adjective-deriving suffix).
Also compare Middle Korean ᄂᆞᆯ압〯다〮 (nòlGǎp-tá, “to be lowly”).
ᄂᆞᆺ갑〯다〮 (nòskǎp-tá)