Somerset Velvet is a paper that has been made for a very, very long time for artists who do etchings and lithography. When inkjet printing became popular with photographers, Somerset began making a version of their old etching paper with an inkjet receptive surface. I tried it years ago, and did not like it. It had poor Dmax, and the prints looked flat.
Later, Epson introduced their Velvet Fine Art paper. I think it is Somerset's etching paper with a different ink receptor coating that works better with Epson's Ultrachrome inks. The Epson Velvet is magnificent, with deep blacks, and beautiful tones for both BW and color printing on Epson printers. I use a lot of it, and have for years.
I have not tried the Somerset Velvet inkjet paper in 15 years, so I do not know if the stuff they sell now is any good. I know that years ago it was inferior to the Epson version.