Jiraiya(自来也,Jiraiya. His name literally means "coming on one's own," which is a description of his personality; quietly appearing and disappearing from Konoha at any time. The kanji on his forehead protector (油, Abura) means "oil."
Jiraiya is named after the character of the same name from Jiraiya Goketsu Monogatari (児雷也豪傑物語, "The Tale of the Gallant Jiraiya"). The Jiraiya in this story excelled in summoning a giant toad (the toad itself was sometimes called "Jiraiya") and toad magic. In that story, Jiraiya and Tsunade were a married couple. There, his name is written as "児雷也" meaning "Young Thunder" which in turn comes from the name Garaiya (我来也, "I came") from the Chinese story Kaishi (諧史).