A derivative of √KUR “skill” in notes from the late 1960s with a difficult-to-read gloss, apparently “a skilful (?device)” according to Carl Hostetter (VT41/10).
Quenya
curo
skillful [?device - tolkien's handwriting was illegible]
curo
noun. skillful (?device)
curo (curu-) noun "a skillful [?device - Tolkien's handwriting was illegible]". (VT41:10)