What is "voord"

The Voord are a fictional extraterrestrial race of mutants portrayed in the British science fiction television programme Doctor Who. Both "Voord" and "Voords" have been used as the plural form. The Voord were conceived by science-fiction writer Terry Nation and first appeared in the 1964 Doctor Who serial The Keys of Marinus. They later appeared in Doctor Who stories in other formats. In one of those stories, written by Grant Morrison, the Voord are revealed to have evolved into the iconic Doctor Who villains the Cybermen.