Also called a Bosom Friend.
Several patterns were published during the Civil War.
And you get the feeling that people followed the patterns
There were crocheted and knotted versions.
Doesn't this one look like tucked fabric
or quilted fabric but most knitters think it is knit.
The shawl seems to have been named for Henriette Sontag (1806-1854) a German opera star.
(Perhaps her shoulders looked cold.)
The Illustrated Magazine gave a pattern for a
"I do not know why it has received the name of the lamented cantatrice Sontag,
but such is the name by which this sort of garment is generally known."
Cantatrice - a singer
Sontag, Habit Shirt and Bosom Friend----- a small shawl
Cephaline - something to wear on your head???
See a patriotic version of a Sontag in the collection of the Massachusetts Historical Society