Because I just saw it yet another time in the Classifieds:
with hands on the hips and elbows turned outward: she stood with arms akimbo, frowning at the small boy.
• (of other limbs) flung out widely or haphazardly.
ORIGIN late Middle English: from in kenebowe in Middle English, probably from Old Norse.
So no, you can't sell a "Akimbo Glock" or whatever; You can't describe using AKIMBO This/That in your loadout. Leave that to COD please!