"Witch" by itself is not always a gendered term as such, but "warlock" generally is - was this distinction made in medieval Europe during the Witch Trials, or did it come about later, after the term "witch" began to refer almost exclusively to women?
According to the Oxford English Dictionary (OED), the root of the word 'warlock' has Old English/Anglo-Saxon roots (i.e. pre-1066), a time when it meant 'oath breaker' or 'traitor'. The OED goes on to say that the word's association with the devil and specifically as applied to a wizard or male witch apparently occurred in the 16th century in Scotland. Although it is possible to document the evolution of the term linguistic changes are less easily explained. It seems clear, however, that the ancient use of the term referring to an oath-breaker took only a small step to be applied to the devil and from those negative supernatural connotations a human oath breaker could become, in the popular mind, someone in compact with the devil.