A Cock is the male representative adult of several S of Galliformes, in particular the cock domesticates. Its female is the Poule. Certain species carry this qualifier in their vernacular Nom like the Coq of heather, Coq of Java, Coq of Lafayette, Coq of Sonnerat. At these species the sexual Dimorphisme is marked enough.
The onomatopoeia imitating the cry of the cock domesticates would be at the origin of the term.