Companion

Those with a familiar are referred to as the familiar's 'companion'. If a familiar's companion dies without them, they are traditionally only referred to as their 'companion'. Using the name of a dead companion in the prescence of their familiar is considered incredibly disrespectful. Once their familiar has also died, however, their real name can be used once more. The same law does not apply the other way around; if a being's familiar dies, they are still referred to by their real name.
See Rogue Familiar for more information about familiars whose companions have died.