Jiraiya, Orochimaru, and Tsunade are the 3 Sannin, so does that mean they were once a group that fought together... or were they just given that title cause they trained under the 3rd and are super powerful, or did the 3rd give them that title cause he trained them...?

On a side note: People need to stop getting mad at those who ask wether it is Sannin or Sennin, ive seen countless people break Sannin down into San meaning 3 and Nin meaning ninja, that is not true, while San does stand for 3 Nin is just a numeric that is used when counting people, its not the same as Hunter-Nin which in that case does stand for ninja, so please stop