We are short of words that contain four us. Among the few that are even relatively common (leaving aside Hawaiian muu-muu) are tumultuously and unscrupulous, although the very much rarer pustulocrustaceous and pseudotuberculous are also recorded.
This term comes from Roman law. Usufruct is the right of temporary possession and enjoyment of something that belongs to somebody else, so far as that can be done without causing damage or changing its substance. For example, a slave in classical Rome could not own anything. Things he acquired as the result of his labour he merely held usus (et) fructus, under “use (and) enjoyment” — it was his master who actually owned them.
The term remains in use in modern US legal practice and elsewhere to mean somebody who “enjoys the fruits” of something, usually land. These days a usufructuary can be a trustee who enjoys the produce or income from property he holds in trust for somebody else. Many Native American groups hold land on a usufruct basis, with rights to enjoy the renewable natural resources of the land for hunting and fishing.