√TŌ/OTO root. “back”
A root in a discussion of prefixes for “back” from around 1959, which Tolkien specified as meaning: “back as an answer, or return by another agent to an action affecting him, as in answering, replying, avenging, requiting, repaying, rewarding”; Tolkien also considered the forms √UTU/TŪ (PE17/166). But Tolkien crossed this all through and seems to have replaced it with √KHAN. Tolkien mentioned the root √OT in a discussion of numbers from the late 1960s, but only to specify that “there was no primitive base OT-” (VT47/16).
References ✧ PE17/166-167, 171, 187-189; VT47/16