You know it as a shorter, simpler way to say “rhinoceros.” But in the 17th and 18th centuries rhino was slang for “money,” and the related adjective rhinocerical was slang for “wealthy.” And no one is sure why.
These are not the rhinos you’re looking for. (But they sure are cool in Black Panther.)
Rhinoceros, from Greek roots meaning “nose-horned,” entered English around 1300; it referred to the herbivorous odd-toed ungulate, two species of which are found in Africa and three in Southern Asia. Rhino- also appears in combination forms such as rhinoplasty (plastic surgery of the nose; first appearance in print: 1828); rhinolaryngitis (1891); and rhinovirus (1961). As the shortened form of the animal name, the word first appeared in print in 1870. But nearly two centuries earlier it was popularly used in England to mean “cash,” and by 1697 the idiom “ready rhino” (or “ready rino”) was in circulation.