A root mentioned in passing in Common Eldarin: Noun Structure from the early 1950s as √SATHA “pair” (PE21/74). It had no derivatives in that document, but might be connected to ᴱQ. satto “both” from the 1910s (PE14/76-77) and Ad. satta “two” from the 1940s (SD/428). In the 1950s document, Tolkien wrote in the margin “Best get rid of s, th [for duals] ?”, indicating he likely abandoned √SATHA.