Either a topographic name for someone who lived on a street corner, from a derivative of corne "corner". From cornet, denoting either a rustic horn or an object made of horn, hence a metonymic occupational name for a hornblower or for a worker in horn. Or a habitational name from (Le) Cornet, the name of several places in various parts of France and in Belgium (Wallonia). Cognate of Cornett.