Oy veh! Kewl was borrowed from martha of flannel and ccc fame.  cool can be
applied to many items, whilst (Br.) kewl! is an exclamatory validation of
extreme fitness for use and native appeal.  BenT is kewl! in manila, but
only cool in SF fog.

As in most linguistics, the meat is in de tails, similar to mudbugs.

pensioner (cunning linguist)