Monier Williams
दुस् ind. a prefix to nouns and rarely to verbs or adverbs (Pāṇ. 2-1, 6; 2, 18 , Vārtt. 2, Pat.; iii, 3, 126 &c. ) implying evil, bad, difficult, hard
[Printed book page 488,2] badly, hardly; slight, inferior &c. (opp. to सु), often = Engl. in- or un- [ID=94676.1]
दुस् [cf. √2. दुष्; Zd. dush-; Gk. δυσ-; Goth. tuz-; O.H.G. zur.] [ID=94676.15]
It becomes दुर् (q.v.) before vowels and soft consonants; दू (q.v.) before र् and sometimes before द्, ध्, न्, which become ड्, ढ्, ण् [ID=94676.2]
remains unchanged before त्, थ् (in older language however ष्ट्, ष्ठ्) [ID=94676.3]
becomes दुष् (q.v.), rarely दुः before क्, ख्; प्, फ् [ID=94676.4]
Surely a mother would name her children after something good?
