Qenya
lopotundo
noun. rabbithole
lopotun
noun. rabbithole
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 word for “rabbithole” appearing in the Declension of Nouns from the early 1930s, a combination of ᴹQ. lopo “rabbit” and ᴹQ. tundo “hole”. In The Etymologies of the 1937, ᴹQ. tundo became “hill”, but the word lopotundo might still be used for the entrance to a rabbit warren, referring to the mound at the entrance rather than the hole itself.