Why is it called pinball?

Originally, pinball machines didn't have flippers (the things at the bottom of the machine that hit the ball). Instead, you would launch a ball into a playfield full of pins and hope for it to land in a hole (like plinko). These pins made the game called "Pinball".
The earliest pinball machines were a wooden playfeild with multiple holes and pins in the board. A ball was dropped at one end and it would bounce on the pins and hopefully fall in the higher scoring holes. This was before electronics, bumpers and flippers.