Clearly this is not the only word to indicate "male's", or things those are belong to males. Comparing with many other similar words, such as "男の", "男性の", this term presents a sort of high sense of popularity. Examples of compound words include "メンズファッション (fashion)", "メンズスタイル (style)", "メンズブランド (brand)", "メンズバッグ (bag)", etc.. A visitor to Japan may often be attracted by such a sign at an elegant department store.
Even though, when I found out a word associated with "What's Today" (Sept. 14th), I am still surprised. "メンズバレンタインデー". This one never join in my vocabulary list by now.