Final answer:
Aven's nickname 'Sheebs' likely stems from her role in caring for a young goat and being part of the shepherding community duties, which in turn associated her with being a shepherd.
Step-by-step explanation:
The nickname 'Sheebs' given to Aven appears to be a result of her association with caring for sheep within her community. In the Andean context where Aven lived, shepherds are highly regarded as they take care of the flocks, which are considered gifts from Pachamama (Mother Earth).
Since Aven was responsible for a young goat and took part in daily care as a symbol of her commitment to the community, it can be inferred that her nickname 'Sheebs' perhaps came from her role akin to a shepherd. In addition, when Aven was introduced to another character, she only mentioned her first name 'Bess' without giving a last name, suggesting that 'Sheebs' could likely be a nickname derived from her interactions or her duties within the community rather than a family name.