But sometimes history was influenced by an effort to look clever (like "deBt" - when there was a perfectly good word borrowed from French dette, but someone decide that the spelling "should" reflect the Latin debitum); and sometimes silent letters were introduced by false analogy. For example, Chaucer used three words 'koude' 'sholde' and 'wolde'; there was no "l" in the first, and there was an /l/ sound in the other two. 'Koude' meant 'had the necessary skill' - which came to be interpreted as 'had the necessary ability'; compare English/French 'He could swim'/Il savait nager. As 'koude' began to be used as a modal, it was felt that it should have an "l" like the other modals 'sholde' and 'wolde - 'false analogy'.
People have tried reforming spelling. Noah Webster had the most success - which accounts for American spellings like 'theater' and color'. My guess is that Webster's spelling reforms worked because there wasn't, in his time, a large mass of documents and written/established practice. Where there is a significant mass of documents/literature, it's hard to get spelling reforms to work - even though they'd make life easier for learners of English as a second language.
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