What was Tom's original name in the first cartoon?

Tom’s original name in the first cartoon was Jasper.

In Puss Gets the Boot, the cat who would become Tom is called Jasper. He is shown chasing an unnamed mouse through a house, while a maid threatens to throw him out if he continues breaking dishes and glasses. The short established the central cat-and-mouse conflict before the characters received their famous names.

The cartoon premiered on February 10, 1940, and was directed by William Hanna and Joseph Barbera for MGM. The mouse was not yet Jerry in the finished film; “Jinx” was reportedly used during pre-production. The name Jerry, along with Tom, appeared in the subsequent short The Midnight Snack in 1941.

Jasper can feel like an obscure answer because most broadcasts, merchandise, and later stories use Tom almost exclusively. It is nevertheless the specific name given to the cat in the first released cartoon, making it the canonical answer to this question.