An adjective appearing as G. ortha “upper” in the Gnomish Lexicon of the 1910s (GL/63), clearly based on the early root ᴱ√ORO¹ having to do with things rising (QL/70). It had an adverbial equivalent G. orthi “up” (GL/63).

Neo-Sindarin: For purposes of Neo-Sindarin I would adapt the adjective as ᴺS. orth “upper”, but for the adverb I would use later S. am “up”.