Actually, tetra means four in Greek. Plegia means paralysis in Greek. Quadri is Latin for four.

In Europe, the term for 4 limb paralysis has always been tetraplegia. The Europeans, being better schooled in the classics than Americans, would never dream of combining a Latin and Greek root in one word. We barbarian Americans coined the term quadriplegia and have used it for years, must to the chagrin of our European colleagues. In the 1990's a movement was begun to change the American term to tetraplegia as well. It has caught on pretty well in the scientific and medical literature, but as you can see, has not reached common use. Even though we use tetraplegia in our publications, etc. it appears that we have not yet had much success in changing terms such as quad rugby, quad coughing, etc. etc. (and doubt we will in the near future).

아마도 이 답이 정답에 가까운 것 같고, 교수는 아마도 머리속으로는 Tetraplegia와 paraplegia의 차이를 묻는 다는 것이 말이 헛나왔을 가능성이 높을 것 같습니다.