What's the name of socks that only show their buttocks and feet and don't wear socks?

Socks with only bottoms and bare feet and no socks are called boat socks.

Boat socks are very short socks, so short that you can't see or only see the edge after putting on your shoes. This material is cotton. Boat socks appeared in the early1980s, when tennis clothes began to rise. The classic style has two fur balls at the ankle, which was popular again in the mid-2000 s, but many styles have been changed, mainly used to match skateboarding clothes, followed by shorts or short skirts. Boat socks are called boat socks because they are shaped like a boat, and they are also called ankle socks or boat socks because they are up to the ankle. In Taiwan Province Province, because you can't see socks after wearing shoes, they are often called "invisible socks".