sou·tane 
(s-tän, -tăn)
(s-tän, -tăn)n.
A cassock, especially one that buttons up and down the front.
[French, alteration (influenced by French sous, under) of obsolete sottane, from Italian sottana, from sotto, under, from Latin subtus, from sub; see upo in the Appendix of Indo-European roots.]