Only Women Are Brunette

The 1953 movie Gentlemen Prefer Blondes featured Marilyn Monroe and Jane Russell as two brunettes who are friends. Perhaps the argument was moot because both the blonde and the brunette get married in the end of the movie. Leaving that aside, you'll notice that the word "blonde" has a "e" at the end of it. That wouldn't be there if a male were the subject of the title. A man's hair color is referred to as blonde with no "e." The spelling is distinct despite the similar pronunciation. Additionally, brunettes receive the same treatment as blondes and blonds in terms of gender.

The feminine form of the word is brunette, which has the "e-t-t-e" suffix. Technically, a man with brown hair is referred to as a brunet. You wouldn't likely notice a change until you saw it spelled out, just like how blonde vs. blond is still pronounced the same. The term isn't frequently used in English, and brown-haired appears to be the preferred way to describe a male with dark hair, while brunette is still favoured for women.