From the root - beber - which means to drink in Spanish. Adding the "se" makes the verb reflexive, hence making the word "to drink oneself."
This had also been proven - sticking a straw in a resevoir of saliva in the side of your mouth, sticking the other end of the straw in the middle of your mouth, and sipping the latter will result in the drinking of your own saliva.
Trying to fend off dehydration, James se bebe saliva.
john cena: "did you see the guys from beberboni?"
johnny sins: "yeah i did there dicks are so big dude"
john cena: "yeah ikr wish my dick was that big then i could be in the beberboni"