Cruk

Cruk was originally a primitive method of constructing a house, using a material similar to dry-stone wall or wattle and daub. The term became associated with the extreme poverty of some of the newer Earth colonies before linguistically metamorphosing into a term of abuse before its final appropriation as a popular human expletive, used amongst the inhabitants of the Terran Federation in the twenty-sixth century as a means of expressing their displeasure (AUDIO: Death and the Daleks). The Seventh Doctor's companion Bernice Summerfield considered it a favourite word of hers and the staff of the Pandora Spindle were rather fond of applying the term profusely during a moment of crisis. (PROSE: Love and War; COMIC: Pureblood, et al)

Behind the scenes
Like 's , the word was a futuristic equivalent of the slang term "fuck", which could be used in exactly the same situations as the contemporary day swearword without causing offence. The term was first invented by Paul Cornell in Benny's debut novel Love and War and has remained associated with the character ever since.