It is said that the current name "Theravada" stems from the fact that, as other sects of Nikaya Buddhism disappeared, a sect of Setsuissaiubu in Nikaya Buddhism renamed themselves 'Theravada' to signify that they were against Mahayana Buddhism, and that the current Theravada is different from the one at the time of the fundamental schism.
現存する上座部の名称は、部派仏教の説一切有部の一派がほかの部派の消滅に伴い、大乗仏教に対立する意味で「上座部」を再度名乗ったことに起源があり、根本分裂のころの上座部とは違うとされている。