Sakasa zuri 逆さ吊り
Upside-down suspension: a suspension in which the tied person hangs head down, often from the legs or ankles.
Jisho.org glosses sakasa zuri (逆さ吊り) as hanging upside down. Shibari Study’s glossary gives it as the term for upside-down suspension, from sakasa, upside down, and tsuri, suspension, and lists kata ashi sakasa zuri for an inverted suspension from a tie on a single ankle. Wikipedia describes inverted suspension as typically lifted from the ankles and notes that it can be hard to hold for long. Its safety section singles out inverted positions as especially dangerous in a fall, since landing on the head from a very small height can cause death or paralysis.