What is ngantoy?

"Ngantoy?" is the Ibaloi equivalent of "Why?".

The word, however, may have been the contraction of the words "ngaran", "to" and "aya". "ngaran=name", "to"=it/his/her, "aya"=interjection for begging a response for a what interrogation..  "Ngaran to aya?" could transliterate to "What is its name?" or "What is his name" or "What is her name?" These questions are figuratively similar to the question of "Why?" or "What did it do to you?" or "What did she do to you?" or "What did he do to you?".

For the specific context of asking someone's name:
"Sipay ngaran mo?" = "What is your name" : "Sipa"="what", "y" =helping verb "is" that is made an inclitic, "ngaran"= "name", "mo"="your"(second person, singular).

For the specific context of asking the names of more than one subjects.
 "Sipay ngaran jo?" = "What are your names" : "Sipa"="what", "y" =helping verb "are" that is made an inclitic, "ngaran"= "name", "yo"="your"(second person, plural).

From some native speakers of Ibaloi, you would hear the query statement "Nganto?" as their way to request a repetition of what you have said.  "Nganto?"="What is it?"