The English language has all kinds of spelling oddities that make it all the more amazing that mere children can do so well in national spelling bees. Most of us can live our entire lives still unsure whether it should be compelling or compeling, concieve or conceive. Why, for example, do we have four, fourteen and forty? Why not fourty?
"Usually in English we strive to preserve the old spelling, at almost any cost to logicality," Bill Bryson writes in The Mother Tongue. He illustrates this with the word ache, which until the time of Shakespeare was pronounced aitch, but only when it was a noun. When used as a verb, it was pronounced ake and spelled the same way. So there were actually two different words spelled differently, pronounced differently and meaning two slightly different things.
In time they were combined into a single word for use both as a noun and a verb, but against all logic, English adopted the verb pronunciation and the noun spelling