Defenition from Websters Dictionary:
: a light loose garment worn especially for protection of clothing while working
I came across this term while reading the Grimm Brothers version of Cinderella. It was used in the first page on the 5th Paragraph.
“They took her beautiful clothes away from her, dressed her in an old gray smock, and gave her wooden shoes.”
The defenition of this word helps understand the story better as it shows that her stepsisters attempted to degrade her as a smock was something used to wear while working and viewed as an inferior piece of clothing.