chemise

1. A woman's loose, shirtlike undergarment. 2. A loosely fitting dress that hangs straight; a shift.
ETYMOLOGY: Middle English, from Old French, shirt, from Late Latin camisia, from Late Greek kamision, probably of Semitic origin. See qm in Appendix II.

http://www.bartleby.com/61/12/C0271200.html

from Late Latin camisia, from Late Greek kamision And, now we also have camisole! Amazing, to think words have lasted so long with so little change!
But I'm also interested in your title: how did "a slip of a thing" get started?

a slip is also a very small plantling. "She's just a little slip of a thing" implies to me that she is very small and slim.

In Spanish:
camisa-shirt
camiseta-undershirt
camisón-nightshirt or nightgown

In Portuguese:
camisa-shirt
camiseta-undershirt, tee-shirt
camisão-nightshirt or nightgown
camisinha-condom
(hey!! [knock-knock-knock] I'm cross-threading here!!