In the Datooga language of Tanzania, to say ‘your mother’ or ‘your father’ to someone can cause offence. Using data from a video corpus of conversational Datooga, this chapter explores these kin-based insults, as well as other affect-laden linguistic practices that invoke kinship relations. Datooga speakers can attest to the truth of something by referring to their opposite-sex parent. Speakers also invoke kin in everyday interjectional phrases, as well as during ritual hunts - a type of speech act known as gíishíimda. Though these speech practices do not all constitute “swearing” in the narrow sense of using “bad” language, they resemble swear words in the way they link speakers’ evaluations of objects in the world with abstract moral values. In the Datooga case, kinship provides the relevant moral framework; the cultural and moral significance of fathers, in particular, makes them good to swear by. From a crosscultural perspective on swearing, I suggest that Ljung’s (2011) “mother” theme be subsumed under a more general “kinship” theme.