People put "an" in front of words that start with H when the H isn't pronounced (like the word, "honor.") you may be thinking, "but what about people who put "an" before words like, "historical?'" Let me explain; the H at the beginning of a word will elide if it falls between two short vowels. If you are talking quickly, and pronounce "a" as a schwa, then the H in "a historical" elides, and so gets pronounced like "an 'istorical." But also remember that this cannot be the case if the syllable to which the H is attached is stressed; for example, the first syllable in "history" is stressed, so people will always say "a history" and never "an 'istory." Hope this makes sense!
sincerely yours,
A fellow meme farmer