rGan Padma-rgyal-mtshan suggested as an etymology of b/rtul zhugs (vrata) the following: “Because one enters (zhugs) into the latter practice/conduct after refining (brtul) the former, [it] is called brtul zhugs” (spyod pa snga ma brtul zhing phyi ma la zhugs pas na brtul zhugs). But perhaps this is ahistorical. One possibility is to understand brtul zhugs as practice that is characterised by “entering (zhugs) into hardships (rtul) or engaging (zhugs) in austerities (rtul),” that is, by taking rtul as having the meaning of “effort/labour” (rtsol ba / ’bad pa), or perhaps “engagement (zhugs) in arduous (dpa’ ba) deeds.” See the Tshig mdzod chen mo (s.v. rtul ba). Cf. also rtul phod.