On Guam, we all say påtas. In the Northern Marianas, the word is addeng. Why the difference?
In the oldest Chamorro dictionary we have (Ibáñez, 1865), before the political separation of Guam and the Northern Marianas, and long before the Chamorros on Saipan (mostly Guam-born settlers) were numerous, and thus before any dialectical differences could arise, the word for "foot" is addeng (in the dictionary, spelled adeng).
Even Pale' Roman's much later dictionary (1932) says it's addeng.
In an old Chamorro hymn, Adios Rainan i Langet, we ask Our Lady to grant us the favor of kissing her feet : Hu gågagao hao Nåna, humitde na fabot, na' nginge' yo' an magof, i dos na addeng-mo. That song is in the Guam hymnal.
Påtas is taken from the Spanish word pata, which means the "foot of an animal." Cats have patas, dogs have patas. But a human being, in Spanish, has a pie. That's pronounced pee-eh, not as in "apple pie."
Addeng is indigenous Chamorro; påtas is Spanish in origin.
In fact, one Spanish author of the 17th century wrote that the pre-Spanish Chamorros showed respect by bowing to a saina (elder) and asking "Ati arin-mo" or "Allow me to kiss your feet." "Arin" must be addeng, spelled the way it sounded to the non-Chamorro ear.
In time, the Chamorros on Guam must have adopted påtas as a slang word even for the human foot, while the Chamorros north of us retained the distinction : påtas for animals, addeng for humans.
This shouldn't surprise us, for even today we see how one person can start to use a word in slang, and before you know it, everyone uses it and the word becomes part of normal speech --- right bro?