Probably fromBrainiaca highly intelligent villain in DC Comics blend of brain and maniac
American Heritage Dictionary of the English Language, 5th Edition
Blend of brain and maniac coined in the Superman comic book. The term first appeared in Action Comics #438 in July, 1958. The word itself is a portmanteau of the words brain and maniac, with influence from ENIAC, the name of an early computer.
Brainiac Sentence Examples
Again, don't fret too much if you don't consider yourself a brainiac.
The dolphin is also symbolic of a variety of things, in addition to being the cutest brainiac in the ocean.
By the conclusion of season five, Brainiac lets loose a deadly virus with the potential to kill millions.
Wait til she finds out how Lex's destiny is about to change thanks to Brainiac.