A noun in The Etymologies of the late 1930s glossed “juice” from the root ᴹ√SAB of the same meaning (Ety/SAB).
Conceptual Development: G. gwâs “juice” from the Gnomish Lexicon of the 1910s is a possible precursor (GL/44).
peich
noun. juice, syrup
peich
noun. juice, syrup
saw
noun. juice
saw
noun. juice
A noun appearing as N. peich “juice, syrup” in The Etymologies of the late 1930s under the root ᴹ√PIS, probably from primitive ✱pisya given its Quenya cognate ᴹQ. pirya (Ety/PIS). Here sy became χı̯ [pixı̯a], the i became e via a-effection [pexı̯(a)], and then the i intruded into the preceding syllable to produce the diphthong ei after the final a was lost to produce peich [peix].
Conceptual Development: Several earlier words seem to be precursors of this one. The Gnomish Lexicon of the 1910s had G. bith “juice, sap” with a deleted primitive form {viđa} (GL/23), cognate to ᴱQ. vite “sap, juice” under the early root ᴱ√VITI (QL/101). Early Noldorin Word-lists of the 1920s had ᴱN. hî “sap, juice” derived from ᴱ✶pisye (PE13/147) with initial p becoming h as was usual in Early Noldorin of the 1920s.
Neo-Sindarin: For purposes of Neo-Sindarin, I would adapt this word as ᴺS. paich as suggested in HSD (HSD), since ei became ai unless it was in a non-final syllable in Sindarin.