There is some conflicting information about this on the 'net, but it appears that sarsaparilla is made from a tropical vine of the Smilax genus. It is sometimes added to root beer and may have been the original "root beer" (with a weaker flavor), but it has no relation to the sassafras tree which is the origin of the root beer flavoring we know today.
I once looked at the ingredients on tapioca, and it just said, "Tapioca". So I called the number on the box for customer service, and they just said, "Tapioca". I made the guy look it up, it took him forever, but he finally told me this long process for converting cassava roots. So I actually knew the answer.
In those days they still had encyclopedias. What I want to know is, did he call customer service for every random question he had about every product, or was this just the one day where he decided to go all in on a whim?