I took a quick peek in my tiny print OED1, and find out that vim is an Americanism. First time in print 1850 and used by itself as an adverb. (I don't have the quote to hand, sorry.) Maybe somebody with access to the OED2 or 3, can take a look and see what the newer scholarship on the word is. OED1 suggested that it was not the acc. of vis but imitative in origin.