Is あれ？ when used like "huh/what?" contracted from something?


I frequently hear 「あれ？」 when people find something that catches their
attention, often even when a listening party is not present. It seems to have
a similar function to "what?", "what's that?", or "huh?".

Since あれ isn't a "question word" itself, was this あれ contracted from a longer
sentence? The closest I could think of is 「あれはなんだ？」, but I'm unsure. If it
isn't from a longer sentence, is there an explanation behind あれ as a question?

I am also interested in if it was historically contracted from something.




I think it's less a question than it is a way to show surprise or confusion.
Also I don't think it's contracted from anything, [this
dictionary](http://www.japandict.com/lists/int) defines it as a [感動詞]{かんどうし}
or interjection which would hint that it's not a contraction of a larger
sentence.

