Diminutive of Cock, which is a short form of Cornelis and Cornelius (for men) and Cornelia (for women). But in other words, you could also say that this name is a variant spelling of Cokkie.This name is predominantly feminine in the Netherlands, especially as an official name on birth certificates. For men, the name is now almost always an informal name.A notable bearer of this name is the Dutch former swimmer Cocky Gastelaars (b. 1938).