This particular version of "akimbo" is derived from Japanese. The word is used in traditional samurai texts to describe a particular class of samurai that wielded two swords, one in each hand. The word acquired its current slang usage via fans of action director John Woo, who used the word to describe his trademark style of wielding two handguns. It has since entered into the computer gaming lexicon as well. (This etymology is mentioned in the book Hong Kong Action Cinema by Bey Logan.)
The traditional English "akimbo" (which you are more likely to find in literature) means "in a position in which the hands are on the hips and the elbows are bowed outward". This version of "akimbo" is generally believed to have come from Old Norse.