ICE stands for "In Case of Emergency".
You put the word "ICE" on the number of the person that if anything happens to you, and rescuers got a hold of your cell, they can directly notify the person that may be directly responsible for you.
Let's say your parents' number, instead of papa? you replace it with "ICE"..in that way rescuers will be able to notify your father right away. Or your landlady's number or something like that...
Sorry mods if naa nay sama ani. I think I posted a similar topic years ago..
links for more info:
ICE Your Cell Phone For Safety - The Early Show - CBS News
In case of emergency - Wikipedia, the free encyclopedia