"nerdy intellectual," by 1986, U.S. teenager slang, from the character Poindexter, introduced 1959 in the made-for-TV cartoon version of "Felix the Cat." The name originally was a surname, said to be Norman.
There is a rare name Poindexter, appearing in French as Poingdestre, "right fist." I have seen it explained as from the heraldic term point dexter, but it is rather to be taken literally. I find Johannes cum pugno in 1184, and we can imagine that such a name may have been conferred on a medieval bruiser. [Weekley, "The Romance of Names," 1914]