RISC is a general category of processors (with the other main category being CISC). There have been dozens of mainstream RISC processors over the last 40 years,

RISC is a general category of processors (with the other main category being CISC). There have been dozens of mainstream RISC processors over the last 40 years, RISC-V is just one that happens to use RISC in the name. Kind of like Microsoft SQL Server, there have been plenty of other SQL database servers in the past but Microsoft decided to use SQL as part of the name.