The narrator of the story is not an English native speaker, but a pre-adolescent Cambodian boy called Arn Chorn-Pond.
He tells us that the weather is cold, we know this because he says: "we huddle back at camp". A phrase that I might have reworded as:
- we huddled back to (our) camp
- we huddled back at/to the camp
Similarly, Chorn-Pond misuses the idiomatic expression teeth chattering and says “bone chattering”; it is not without sense because our bodies do shiver in the cold, but we don't hear the noise of our bones "chattering". We hear our teeth knocking against each other.
The correct and idiomatic expression is
Later in the story the narrator adds:
But they don't pay attention, they only want to talk to themself or maybe sleep. Later, the head guy, he walk past our group; now everyone asleep but me
It is a type of pidgin English, obviously Arn Chorn-Pond has some knowledge of the English language but his speech contains a fair number of grammatical errors in standard English.
Never Fall Down tells the story of the Khmer Rouge and the murderous genocide they wreaked upon their own people of Cambodia. When the Khmer Rouge came to power in 1975, Arn was a nine year old boy living in Battambang, Cambodia with his family
Source: Libris notes