cassockyoudaoicibaDictYouDict[cassock 词源字典]
cassock: [16] Etymologically, a cassock is probably a cloak worn by a Cossack; the two words appear to be ultimately identical. Cassock, which originally meant simply ‘cloak’ or ‘long coat’ (its current application to clergymen’s tunics arose in the 17th century), comes via French casaque from Italian casacca. It has been conjectured that this was a descendant of Turkish quzzāk ‘nomad’ (a derivative of the verb qaz ‘wander’), which also, via Russian kozak, gave English Cossack [16].

However, another theory is that cassock comes ultimately from Persian kazhāghand ‘padded jacket’, a compound formed from kazh ‘raw silk’ and āghand ‘stuffed’.
=> cossack[cassock etymology, cassock origin, 英语词源]
cassock (n.)youdaoicibaDictYouDict
1540s, "long loose gown," from Middle French casaque "long coat" (16c.), probably ultimately from Turkish quzzak "nomad, adventurer," (the source of Cossack), from their typical riding coat. Or perhaps from Arabic kazagand, from Persian kazhagand "padded coat," from kazh "raw silk" + agand "stuffed." Chiefly a soldier's cloak 16c.-17c.; ecclesiastical use is from 1660s.