Geek \GEEK\ , noun;
1. A computer expert or enthusiast (a term of pride as self-reference, but often considered offensive when used by outsiders
2. A peculiar or otherwise dislikable person, especially one who is perceived to be overly intellectual
3. A carnival performer who performs sensationally morbid or disgusting acts, as biting off the head of a live chicken
I had no idea this word fell into the 'freak' category until I saw it in a book I'm reading that's set at the end of the US Civil War. In the book the character was talking about it in terms of a geek in a carnival. Turns out, that while this word is old enough to be appropriate for the time period, that definition is not.
Geek is first attested in 1876 with the definition "a fool; an uncultivated person; a dupe." It's probably a variation of geck ("a fool, simpleton") which dates to the mid-1500's and comes from Low German geck. Geck is derived from an imitative verb in North Sea Germanic and Scandinavian that meant "to croak, cackle" and "to mock, cheat." Geek in American slang dates to about 1919 and referred to performers who did particularly gross acts (think Ozzy Osbourne and that dove). In the 1980's geek took on its current meaning as a slang term for a socially awkward person who is obsessed with and/or particularly talented at new technology and computers.