The term "trunk sale" or "trunk show" has its roots in Europe duriing Medieval times. Many of the smaller villages had few options to purchase goods. Traveling merchants would arrive with trunks full of fabrics, clothing and shoes and sold their wares out of these trunks to the masses.
It was always a special event when an advance courier would arrive in the village to announce the upcoming "Trunk" show.
According to Webster's, trunk is defined as a (1) : a large rigid piece of luggage used usually for transporting clothing and personal effects. (Quite Obvious")
This term, to me, know means when the Allen Edmonds rep shows up twice a year at a local men's store for the "trunk sale". They merely have every model of shoe to look at and order. Unfortunately, the shoes are sent to you because, many times, they are not stocked at the merchant.
During these "Trunk Sales" a discount is generally offerred.