The expression had became a popular saying by the 18th century. Feasting wasn’t done regularly in the 18th century unlike the middle ages which it was done constantly for battles won but by the 18th century this rare tradition had become more common and even an art. The core of this event was drinking wine among many other things. The people throwing the feast would give toast to others and give them presents sometimes. When the host toasted for someone, most of the time it was for a beautiful women, if the beautiful women agreed to the toast, they would then become the toast of the town.
Now these days this expression is used for a variety of meanings, like if a director has a successful film with a film actor the media will say ” the director has made the actor into the toast of the town.