There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
mathron
noun. herd, herdsman, shepherd
nethron
noun. herd
A noun appearing as {nestor >>} nethron “herd” in the Gnomish Lexicon of the 1910s, clearly derived from the early root ᴱ√NESE “give to feed; feed, pasture; graze” (QL/66) with sr becoming thr.
Neo-Sindarin: The suffix -(r)on is mostly an agental suffix in later Sindarin, so I would adapt this word as ᴺS. nethor “herd, flock” for purposes of Neo-Sindarin from the Neo-Root ᴺ√NES and primitive ✱nes-rē; compare [N.] tathor < ᴹ✶tathrē.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A noun in the Gnomish Lexicon of the 1910s glossed “herd, herdsman, shepherd”, an agental form of G. moth “sheep”, with a variant mastir which is probably the feminine form “✱shepherdess” (GL/56). The gloss “herd” is reinforced by the fact that Tolkien equated it to G. nethron “herd” (GL/60).