Here’s an interesting story about the words Chaucer contributed to English (also, this link). I had heard earlier about the significant contribution Shakespeare made to our lexicon, but I wasn’t aware of Geoffrey’s additions. While I’m citing these two language influences, I’ll also mention some of the contributions of the King James Bible.
Also, this story about clues to pre-recorded-sound-era pronunciations mentions Chaucer, too, but it also points to one of the issues I notice in my own writing: that the longer I’ve been teaching poetry, the most attention I find myself paying to the sounds of words, the worse my spelling has gotten. That is, my spelling has become less graphically correct but more phonemically correct — I’ve even caught myself freewriting “won” when I heard my mental voice say “one.”