1. Far exceeding the usual size, amount, degree, etc.; extraordinarily large or extensive; immense: The manager decided not to undertake an expansion of the grocery store because of the enormous costs that would have to be made.
2. Etymology: from Latin where the norm- root appeared after the prefix e- (a variant of ex-), meaning "out of", resulting in enormis, literally "abnormal, irregular".

The term acquired the specific sense of departing from the "norm" by being much larger in size than usual; that is, "huge" which is now the most common meaning of the English descendant of enormous.