As a given name, it was used on the American sitcom Murphy Brown (1988-1998) for both the mother and son of the main character. By 1998 it was more popular as a name for girls in the United States, perhaps further inspired by a character from the movie Jerry Maguire (1996).
In modern English, zenith means "the highest point or state; peak" and in astronomy, refers to "the point in the sky vertically above a given position or observer" or "the highest point in the sky reached by a celestial body."
In the English-speaking world, this name has been in occasional use from the late 19th century onwards.