Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!

Qenya 

nasse

noun. thorn, spike, spike, thorn

A noun for “thorn, spike” in The Etymologies of the 1930s under the root ᴹ√NAS “point, sharp end” (Ety/NAS).

Neo-Quenya: For purposes of Neo-Quenya I would use this word for “spike”, but for “thorn” I would use other words like [ᴹQ.] ecco or necel.