Hojōjutsu
“the art of the capturing rope” — ho, to capture; jō, rope; jutsu, art or technique
The historical Japanese martial art of restraining prisoners with cord, sometimes cited as an ancestor of modern rope bondage.
Hojōjutsu is a genuine martial discipline, taught within several koryū schools, concerned with restraining a captive using cord. It developed in a context where binding a prisoner communicated their rank and alleged offence, so its forms are functional and highly codified.
The honest version of the lineage claim
You will frequently read that modern rope bondage descends directly from hojōjutsu. The connection exists, but it runs through a small number of twentieth-century figures — most often cited is Itō Seiu — who drew on historical restraint imagery for artistic work, rather than through any continuous transmission of technique. A great deal of what is taught today was developed much more recently than the lineage claim suggests.