What does ‘Sannin’ mean in Naruto?

Sannin ⇒ 

It mean’s ‘three ninja’. It’s use as a way to refer to the Densetsu no Sannin, which is to say, the Legendary Three Ninja’s. This was the predication given by Hanzoo the Salamander to Jiraiya, Orochimaru and Tsunade in the Second Great Shinobi ninja War, as a sign of the respect to acknowledge that they were not easy for him to kill. They got this title in the 2rd Ninja war because of their achievement’s and over whelming power.

Ninja’s who possess unmatched strength and the skill are ranked right below that of a Kage. A maximum of three Sannin per village are appointed by each Kage. Sannin’s no longer Wear the forehead protectors or vest’s, in Order to blend in with the common civilian’s. They are emitted to a perform Dangerous S-Class missions. That just seems to prove that it is merely a title and not a actual “class” of ninja that one can be attain through normal means.

In Japanese the word “San ()” mean’s three (3). The word “Nin (人)” mean’s person. Ergo, “Sannin (人)” means three people. Jiraiya, Orochimaru  and Tsunade received the title of The Legendary Sannin from Hanzo the Salamander during the Second Shinobi ninja War. “The Sannin” just quite literally translate’s to the, “The Three (people).” But if I could make one small addition in, possibly the most common form of a Japanese humor are puns. Because the language has been such a limited amount of sounds, often word’s will have more than one meanings. In this case, as I stated earlier, the term are literally translate to, “The Three (people)” as the”三”+”san”+”3″ and “人”+”nin”+”[counter for] people.” However also, since puns they are a regularity for the culture, and considering the setting for the series, maybe “nin” would have a double meaning as it is also short for “ninja.”

Fun fact: The story of The Legendary Sannin’s comes from the Japanese novel called The { Tale of Jiraiya the Gallant} Sound familiar? That’s because the episode in which Jiraiya’s dies is named after the that novel.

As the other’s have pointed out, Sannins are literally mean Legendary Three Ninja’s.They are Orochimaru, Tsunade, Orochimaru and Jiraiya. As a genin, the three were the student’s of Sarutobi Hiruzen, the 3 Hokage. Despite being a team and having accomplishe great thing’s together, the three members were always in the constant disagreement with one another, which means Tsunade referred to as a “three-way deadlock”. Once they became skilled ninja’s able to look after them selves, Hiruzen’s team was disbanded. Despite the official dissolution of their team’s, the three continued to work together during the Second Shinobi ninja World War. During one battle with the Hanzo of the Salamander, they were the only hidden leaf ninja to survive Hanzō’s attacks. As a reward for that, Hanzō dubbed them “hidden leaf’s Legendary Sannin”

It also seems to have there some connection to their summoning jutsu (slugs/toads/snakes). Naruto and Jiraiya both demonstrate an ability to use the Sage Jutsu after having trained with the frogs.