In the 1987 Teenage Mutant Ninja Turtles cartoon, Splinter used the human name Hamato Yoshi before becoming a mutant rat.
The cartoon’s backstory identifies Hamato Yoshi as a martial-arts master who was forced to leave Japan after a conflict involving Oroku Saki. Yoshi later lived in New York City’s sewers, where exposure to mutagen transformed him into Splinter. He then raised and trained the four turtles after they were changed by the same substance.
Hamato Yoshi is also the name used for Splinter in several other versions of the franchise, although details differ between continuities. In some adaptations, Yoshi’s relationship with Saki, his teaching history, and the exact circumstances of the mutation are revised.
The name is not the same as the turtles’ names, which come from Renaissance artists. “Splinter” is his adopted identity and reflects the character’s role as a teacher who helps the turtles master ninjutsu.