Mount Sapo

Mount Sapo is a fictional mountain supposed to exist somewhere near Rome, presumably in Italy. It appears in a fanciful rewriting of the history of soap, and it is often claimed to explain the origins of the name. The tale occurs in a number of online sources, including the website of The Soap and Detergent Association.
The story about Mount Sapo explains that upon its slopes, ancient Romans used to sacrifice animals as burnt offerings. Wood ash from the fires of their altars mingled with the grease from the animal sacrifices, forming a primitive kind of soap. This soap found its way to the clays of a nearby stream, where local people found that it helped them get their laundry cleaner. Soap gets its Latin name, "sapo", from the name of the mountain. 
This narrative is probably a hoax. There are many reasons to find it improbable: 