[talideon]

There's nothing even slightly strange about it. The terms are self-recapitulating because parents mistake children's babbling for first words. If anything, it'd be strange if they weren't the same. Take a read of this: http://languagehat.com/trask-on-mama-and-papa/

[talideon]

Addendum: in case anybody's wondering what I meant when I wrote "it'd be strange if they weren't the same", I was referring to the high probability of them being coincidentally the same or at least very similar.

[ptaipale]

Then why isn't aunt "gaga" in all languages?

[talideon]

Why would it be? What's your reasoning for expecting it to be? Did you read the paper linked to?