In a Irish Pub, a small private room at the end of the bar, for a lady to drink a pint privately, and not be seen by the male patrons. Mainly late 1800s-early 1900s.
When a woman went into a Pub for a nip or a pint, she would be seated in a snug for her privacy. A man having a pint with his wife would also be seated in a snug.