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.
Gnomish
ortha
adjective. upper
antha
adjective. upper
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”.