Tatami is already a Japanese word.
tatami
"Tatami" in Japanese, is a japanese style flooring that is often used in Japanese homes and "dojo" (training hall). I am in karate so this is why I know some words in Japanese, plus I am taking lessons in the Japanese language.
Tatami is a type of Japanese flooring made from rice,straw with a covering of woven soft rush straw.
In traditional Japanese homes, tatami mats are a kind of rush flooring, and for sleeping on.
In japan, mat is Tatami and we just call it Judo Tatami.
Tatami.
Floor mats in traditional Japanese homes are called Tatami Mats.
Tatami mat
Tatami.
The matting is called a tatami and they are generally made from rice stalk straw.
The term Ryokan means a traditional Japanese inn or a small hotel. Since these are traditional Japanese inns, the guest living there had to sleep on the floor with their tatami prepared for them.