From Proto-Germanic *smalt- (to melt, fuse vitreous glass onto metal), through Frankish into Old French esmail, into Middle English by the 14th century — a craftsman's term for fired glass glaze that later, by visual analogy, named the hardest substance the human body makes.
A hard, glassy coating fused onto metal, glass, or ceramic surfaces by firing, or the similarly vitreous substance forming the outer layer of a tooth.
The English word 'enamel' derives from Anglo-French and Old French 'esmail' (also 'esmael', 'esmal'), meaning a vitreous glaze fused onto metal surfaces. The Old French form derives from a Frankish or Old Low Franconian source, reconstructed as *smalt- or *smeltjan, cognate with Old High German 'smalzjan' and the root of modern German 'Schmelz' (enamel, glaze) and 'schmelzen' (to melt). The Frankish *smalt- traces to Proto-Germanic *smeltaną (to melt, to smelt), derived from Proto-Indo-European *mel- (to soften, to crush, to grind). The PIE root *mel- is extraordinarily productive: it underlies Latin 'molere' (to grind), Greek 'mýlē' (mill), English 'mill', 'melt', 'smelt', 'mild', and 'mollify'. The word entered Middle English as 'enamailen' (
The French word for enamel — émail — is spelled identically to the French word for electronic mail (email), a collision invisible in speech but jarring in print. More striking is the medical transfer: when 17th-century anatomists called the outer layer of teeth 'enamel', they were making a technical analogy. They genuinely believed the microscopic structure