Achsah is Caleb's daughter. She is put on the marriage block when Caleb wants someone else to fight his battles in Canaan for control of his land from wandering tribes. That's just how we imagine we'll get married someday…sigh. So romantic.
Othniel, Caleb's brother, steps up to the plate and wins the battles required to win the hand of Achsah in marriage. Okay… maybe that's not how we want our wedding to go.
Achsah, being a clever woman, requests that she be given easy access to springs because her region is very arid. Caleb grants her request despite the fact that women were considered not to have rights during this time (15:13-19).
Moral of the story: even though you have to marry your uncle, you can still be an empowered feminist.