Hi,
I believe it was Thomson. The model was called ‘plum pudding model’ because he described the atom as a larger positive mass in which small negative particles, the electrons, could be found, the same way small dried fruit pieces are found in a plum pudding.
Hope this helps! If my answer was not clear enough or you’d like further explanation please let me know. Also, English is not my first language, so I’m sorry for any mistake.