What words change meaning when the first letter is capitalised? The only word with this property that comes to mind is polish.
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I can't think of any other word that changes its meaning so completely. Most often, a word changes because a noun becomes a proper noun, usually either a brand or a place where something commonly known originated. The Polish/polish pair is different; the proper noun (adjective actually) has nothing to do with the common noun.
EDIT: For posterity, the term for these words is "Capitonym"; more information and a lot more examples are here at Annie's Annex.