Castration Anxiety
Castration anxiety is a Freudian concept in which a child is afraid their genitalia will be harmed by the parent of the same sex as retribution for sexual feelings for the other parent. It is both a literal (fear of actually losing genitalia) and metaphorical (symbolic representation of genitalia) fear that arises due to the Oedipal complex. This can occur in both males and females and presents itself during the phallic stage (occurring between the ages of 3-7).
For example, a son fears his father will damage his genitals because of his sexual feelings towards his mother.