This name is not going to make much sense when and if 170 is incorporated into R7RS-large, in which case it will probably be called (scheme posix) or (scheme posix core) or something of the sort.  Perhaps this facility should be migrated to SRFI 198 as well and called simply "posix-error".  That way any Posix-related SRFI can raise it and any of their callers can check for it.