A well-known example of a current lexical contrast between presentday Belgian and Netherlandic Standard Dutch is the heteronymy between the nouns nagel (BD) and spijker (ND), referring to a metal pin. In this contribution the diachrony of the lexical pair nagel/spijker, occurring both as single nouns (appellatives and proper names) and in idiomatic expressions, is investigated. The distribution of modern family names with nagel/spijker ‘nail’ reveals that nagel indeed was commonly used in Flanders and spijker in the Netherlands, but as nagel also occurs in certain parts of the Netherlands, this noun must formerly have been in use in the Netherlands as well. An overview of the historical development of nagel/spijker shows that in Middle Dutch nagel was the common word for a metal pin in the entire language area. In the New Dutch period however, in northern Dutch the noun spijker superseded nagel in its general meaning, whereas nagel took on a specialized meaning in craftsmen’s circles.