forbidden variable in for loop.

[Ray Andrews <rayandrews@xxxxxxxxxxx>]

Gentlemen,

  for a in *; do echo $a; done

All fine. but:

  for i in *; do echo $i; done

Gives me a list of zeros. Followed by "zsh: bad floating point constant"

It works fine for any letter of the alphabet so far tested except 'i'.  
For the life of me I can't guess what it is that makes 'i' special. Any 
thoughts?