Ohhhhhh, that actually finally makes some sense. From straightdope.com (through digg.com )
Mainly to continue the tradition of making English as incomprehensible as possible, thereby keeping the spelling bee industry in business. (Believe me, there’s millions in it.) Colonel comes from Old Italian colonello, commander of a column of troops, which in turn derives from colonna, column. It wasn’t always spelled the Italian way, though. Four hundred years ago English followed the Spanish practice and spelled the word “coronel,” sensibly pronounced the way it looked. Eventually this was corrupted to ker-nel, still not bad considering we’re talking about the British, who pronounce “Featheringstonehaugh” “Fanshaw.”
But it couldn’t last. Some nameless busybody decided coronel ought to be spelled “colonel” to better reflect its Italian origin, doubtless out of the same misplaced love of precision that gave us 16-1/2 feet to the rod and 27 and 11/32 grains to the dram. It’s just the Anglo-Saxon way, I guess. How these people conquered an empire I’ll never know.
–CECIL ADAMS
