Anagram

An anagram was a word or phrase created by rearranging the letters of another word or phrase.

When adopting a false identity, the Master sometimes used an anagram. In 13th century England he went by Sir Gilles Estram, and on the starship Gallery he used Mr Seta. Each was an anagram of 'Master'. (TV: The King's Demons, AUDIO: Dust Breeding)

The Mimic's inability at original thought caused it to use anagrams. When it merged with Francis Pearson, it used the names Persona and Sperano, both anagrams of Pearson's last name. Even the name it became known by, Managra, was an anagram of 'anagram'. (PROSE: Managra)

SenéNet was a computer company on Earth. The name was an anagram of "Nestene" which was secretly in charge of the company. (PROSE: Business Unusual)

Behind the scenes
Roy Tromelly was a pseudonym used to conceal the identity of actor Terry Molloy in TV: Remembrance of the Daleks, so as not to spoil early that the Emperor Dalek was in fact Davros. It is an anagram of Molloy's name.