first off does the word sanin mean anything like 3 something?

I guess what makes the sanin the legendary sanin?
Did they go on a mission/ quest or because they are really strong? and who gave
them that title in teh first place.

On the one hand i can't see how jirarya made it to be sanin. His flash backs shows he's
a stubborn and regular ninja, like naruto. I guess he matured with age but he still goes for the
girls and drinks.

Must be something they did or they saved teh village or something back then.
but i will say they are some of teh strongest in konoha as of now excluding orochimaru.


And why can only they and the 3rd mess around with naruto's nine tails seal?