'moustache' originates from French, specifically the word 'moustache', where the form was borrowed into English (through French) referring to facial hair on the upper lip.

'moustache' changed from Italian 'mostaccio' and Medieval Latin 'mustacium' and ultimately from the Ancient Greek word 'μύσταξ' (mýstax); these forms evolved through Romance languages into the modern English 'moustache'.

Initially it referred to the hair of the upper lip ('moustache' / 'mýstax'), and over time the meaning has remained largely the same, continuing to denote the same feature of facial hair.