This one can be definitely dated to 1902, when it appeared in Butterick's Delineator magazine.
We've seen the term "sack" used before for Banner Sack Apron 131 to describe a relatively unstructured garment that hangs from the shoulders. (The French spelling of "sacque" tends to remind one less of a sack of potatoes.)
Here's a very funny discussion of the uses and abuses of dressing sacks, published in 1913 by Myrtle Reed in her book Threads of Grey and Gold:
The dressing sack is (supposed to be) a garment you wear while you dress you hair; it keeps hair off your clothing but more importantly, it's loose enough so that you can raise your arms up high enough to reach behind your head, which is not possible in most ladies' garments until the 1920's, when women's clothing lost much of its confining structure, and when, incidentally, women started bobbing their hair.
Dressing sacques don't seem to show up much past World War I.
However, notice that Reed recognized that dressing sacks are sometimes worn as bed jackets, which will start to show up in great variety in the 1930's, and are still offered now and again as an option in robe patterns, pointing right back to Reed's idea that a dressing sack is nothing more than a Mother Hubbard cut off at the hips. Both are suitable for maternity wear.
This also strikes me as a supremely practical garment to wear when reading in bed when one has a drafty bedroom and a limited heating oil budget.