A verb for “to try” based on the root √NDEB in notes from the 1960s (PE17/167). As suggested by Christopher Gilson, this appears to be a draft of Tolkien’s attempt to define the phrase “try harder” in Quenya. Of the root √NDEB, Tolkien said it “too obviously = endeavor”, and he wrote another root √RIK below it, with a Sindarin verb form ritha- or raitha. It seems Tolkien here changed √NDEB >> √RIK, but in later notes from 1969 Tolkien had the root √NDAB “endeavor, try, seek opportunity” (PE22/151), indicating that the concept of √NDEB was not entirely abandoned.

Neo-Sindarin: For purposes of Neo-Sindarin, I would mainly use ritha- for “to try (put forth effort)”, but I think dev- is worth retaining with a different connotation: “to try, *seek opportunity, experiment”. In other words, you use ritha- “try” when you are uncertain whether you are capable of performing the action, and dev- “try” when you know you are capable, but are uncertain what the result of the action will be.