The Law of Consonantal Shift was a principle that was developed by the Brothers Grimm. The law proposed that language changed over the course of centuries as words changed in a consistent fashion.
The Fourth Doctor mentioned this to Romana II when discussing how the names of the Hydrax's officers, Miles Sharkey, Lauren MacMillan and Anthony O'Connor, had changed to Zargo, Camilla, and Aukon. (TV: State of Decay)
When Paradise Towers fell into ruin, the names of some of the groups mutated. The gangs of girls who roamed the corridors became known, even to themselves, as Kangs and the residents became know as Rezzies. (TV: Paradise Towers)