An adjective appearing as G. ortha “upper” in the Gnomish Lexicon of the 1910s (GL/63), clearly based on the early root ᴱ√ORO 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”.
An adjective in the Gnomish Lexicon of the 1910s glossed “upper” based on (and grouped with) G. am “up, upwards, towards head of” (GL/19). It had adverbial equivalents G. anthos “up, above” and G. anthum “upwards, cg. onto”, but these seem to have been rejected.