Are yams and sweet potatoes the same?
Figuratively, anything that is beyond criticism: “That housing project is a real sacred cow: the city council won't hear of abandoning it.” In India, followers of Hinduism consider cows sacred and do not eat them because they believe the animals contain the souls of dead persons.
Someone or something that may not be questioned or altered: Everything is on the table. There are no sacred cows
[1910+; fr the venerated status of cows in Hinduism]
in Hinduism, the belief that the cow is representative of divine and natural beneficence and should therefore be protected and venerated. The cow has also been associated with various deities, notably Shiva (whose steed is a bull), Indra (closely associated with Kamadhenu, the wish-granting cow), Krishna (a cowherd in his youth), and goddesses in general (because of the maternal attributes of many of them).