Thanks a ton, Renaissance scholars/teachers. Why is there a b in the words debt and doubt? Turns out it's a Renaissance thing. Teachers at that time decided that Latin was more scholarly than French, from which we actually got use of those words. They were already words in English, borrowed from French, sans b. However, the teachers decided that they wanted to go back to the Latin roots (from which the French got them) and spell them using those Latin roots, but to go on pronouncing them their English way. This, and a whole lot more examples like them, is why English doesn't sound like it looks. Well, that and the Great Vowel Shift that took place just before Shakespeare's time, before which line and join rhymed, and knight was a two-syllable word in which the k was pronounced.
Can you tell I've been listening to my "History of the English Language" class? It's really just fascinating!