grim face; stern look; severe expression
Describes a facial expression that is harsh, forbidding, or unfriendly, often due to anger, worry, or determination.
He entered the meeting room with a grim face.
With that stern look, he seems to have something troubling him.
Compound of 険しい (steep, severe, grim) and 顔 (face). The exact historical derivation is uncertain, but the phrase is a straightforward combination of its components.