Though plastic sushi grass is a modern development, the idea behind it has been around for centuries. Flowers, leaves, fruits and branches have been used to line vessels in Japanese cuisine for over a millennium, according to Nancy Singleton Hachisu, a James Beard Award–winning food journalist and an expert in authentic Japanese cuisine.
The use of leaves to separate food, however, became common during the Edo period (1603–1864). “Originally, the Kanto region (around Tokyo) used sasanoha [leaves from the bamboo plant], while the Kansai region (around Kyoto) used haran.”
It’s the right word.
The acids denature the proteins causing them to become firm and opaque just as if they had been cooked.
There are some dishes, like Ceviche, that use this effect intentionally (“cooking” fish in lemon juice).