Mien is somebody's bearing and manner. A grave mien, of noble mien, his cheerful mien.
It is said like mean and is literary to the point of being archaic. It names how somebody carries themselves rather than what they look like, which is why it belongs with words such as bearing.
1nounmienSomebody's bearing and manner.
“The judge had a stern mien that made even the lawyers nervous.”
mien is a bearing.
French mine means appearance, and the English form was influenced by demean and demeanour.
French
mine — appearance
English, today
mien
Built from
From French mine (“appearance”) (whence also Danish mine and German Miene), perhaps from Breton min (“face of an animal”), or from Latin minio (“to redden”).
Etymology from Wiktionary, CC BY-SA
Practised in A Song of Ice and Fire