A verb appearing as G. rin- “(intr.) revolve, return, come back; do again” in the Gnomish Lexicon of the 1910s (GL/65), based on the early root ᴱ√RINI having to do with circles (QL/80).

Neo-Sindarin: The root ᴹ√RIN was still associated with circles in Tolkien’s later writings, so I would retain ᴺS. rin-, but only in the limited sense “to revolve” = “*to circle round”. For “return” I would use the later verb dandol-.