སྙིང་རུས།

The etymology of snying rus “firmness of mind (heart), i.e. diligence, zeal, perseverance” (Jäschke 1881: 189) is “heart’s bone” (snying gyi rus pa). See also the Padma bka’ thang (p. 664): ngu pas mi phan snying la rus pa gyis ||. Note that thugs rus (honorific) is recorded in  Jäschke 1881: 189 but not in the Bod rgya. Cf. also sdug rus byed “to struggle.”