The Quenya name of S. Orodreth in some of Tolkien’s later writings (PM/350). This name was Sindarized as S. Rodreth (Arta- > Rod- and -resto > -reth), and then further modified to Orodreth “because of his love of the mountains” (PM/350). The initial element of Artaresto is the prefixal form arta- of arata “noble”. An alternate Sindarin form might be Arodreth “Noble Endurance” (PE17/182), suggesting its second element resto might be based on √RETH “remain in same place” and mean “endurance”; hat-tip to Vyacheslav Stepanov for this suggestion.

Conceptual Development: In later notes, his Quenya name was changed to Artaher and his Sindarin name to S. Arothir, but these changes were not made in The Silmarillion narratives and the status of these later names is unclear (PM/350).