Qenya
káro
noun. doer, actor, agent
tyaro
noun. doer, actor, agent
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!
A noun in The Etymologies of the 1930s glossed “doer, actor, agent” derived from the root ᴹ√KYAR “cause, do” (Ety/KYAR).
Conceptual Development: In an earlier version of the entry for ᴹ√KAR “make, do”, Tolkien had ᴹQ. káro “doer, actor, agent” (Ety/KAR; EtyAC/KAR), but this form was abandoned when Tolkien decided ᴹ√KAR meant only “make, build”.
Neo-Quenya: Despite the later restoration of the sense “do” to the root √KAR, I would stick with attested tyaro for “actor, agent”, since Q. tyar- “cause” continued to appear in Tolkien’s later writings.