A verb for “bow” based on the root ᴹ√KUB, appearing in the Quenya Verbal System from 1948 (PE22/102).
Qenya
kumbe
noun. mound, heap, mound, heap, [ᴱQ.] pile; load, burden
kuv-
verb. to bow, to bow [the body]
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.
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 Etymologies of the 1930s glossed “mound, heap” derived from the root ᴹ√KUB (Ety/KUB). It is a later iteration of ᴱQ. kúme or kumbe “a pile, heap, load, burden” from the Qenya Lexicon of the 1910s where it was a derivative of ᴱ√KUMU “heap up” (QL/49). Its Noldorin cognate N. cum appeared in the name N. Cûm-na-Dengin “Mound of Slain” in Silmarillion drafts from the 1930s (SM/312, LR/147), but later this name became S. Haudh-en-Ndengin.
Neo-Quenya: For purposes of Neo-Quenya, I’d avoid this word and use Q. hamna instead, the cognate of S. haudh. In later writings the root √KUB was given the new meaning “hide, secrete” (PE22/155).