K is for Kappa
Kappa is the tenth letter of the Greek alphabet - pretty clearly where the modern letter K comes from.
But a Kappa is also (among other things) the name of a fabulous beast: a sort of water-sprite in Japanese folklore. Kappas are troublesome or downright evil reptilian creatures that lurk in ponds and rivers. Perhaps their coolest feature is the bowl-shaped indentation on the tops of their heads. When they are away from their pond or river, this bowl has to remain full of water at all times, otherwise they freeze and can't move.
So, if you ever find yourself pursued by a rampaging Kappa, just make it spill the water out of its head and you'll be perfectly fine.
See, don't say I never give you useful information ...
Archaeopteryx Blunderbuss Chthonic Dreadnought Entropy Fulgurite Gargantua Humbucking Ichthyic Juggernaut Kappa