And an elephant... a chair! I always say it but never knew it was "an" rather than "a" because of the noun starting with a vowel.
Did you know that "a newt" (in Russian, тритон) was originally "an eft" and "a nickname" (кличка) was "an ekename"? Going in the opposite direction, "an apron" (фартук) was historically "a napron", which was cognate with "a napkin" (салфетка)

(There are even more examples of the letter "n" splitting from the indefinite article and falsely attaching to the noun, or vice versa, but these are the few I can remember right now.)