triumvir (n.) Look up triumvir at Dictionary.com
"one of three men in the same office or of the same authority," mid-15c., from Latin triumvir, from Old Latin phrase trium virum, genitive plural of tres viri "three men," from tres "three" (see three) + viri, plural of vir "man" (from PIE root *wi-ro- "man"). The Latin plural was triumviri.