Blue Bloods' title includes a double meaning of sorts. On one hand, it points to the fact that each member of its central cast works in law enforcement. Simultaneously, it evokes the fact that each of its main characters is related to one another. Thus, "blood" refers to both the professional and familial identities of its protagonists.
The members of the Reagan family at the series' core all work a different profession under the law enforcement umbrella. Tom Selleck's Frank Reagan, for example, is the commissioner of the New York City Police Department. His daughter Erin Reagan (portrayed by Bridget Moynahan), meanwhile, is an assistant district attorney. Storylines that see different family members at their respective jobs ultimately coalesce at their Sunday dinners, a weekly Reagan family tradition.
Those Sunday dinner scenes are the lifeblood, so to speak, of Blue Bloods. By providing a domestic environment in which developments both personal and professional can come to a head, Blue Bloods' family dinners unify various character and plot threads alike. While the meal therefore isn't generally the focus, each dinner scene nevertheless allots a full serving of food to each attendant character. Among the central cast members, Moynahan is notable for her skill at feigning eating what's on her plate rather than actually consuming the food in front of her.