There is always a little hubbub around the label “viking,” as many people think vikings were a people, which is not true. Viking is a verb, not a noun. The adventurers were Norse people, some of whom went raiding by sea, an activity referred to as viking. The Viking Age could more accurately be thought of as the Raiding Age of the Norse people. However, to call this a viking chest might not be entirely incorrect. There are theories that these chests were brought on longships to both serve as storage and seating for oarsmen and that the trapezoidal construction provided stability against both tipping and racking while traversing rough seas. As with most theories about the Viking Age, with the complete lack of written history, this theory is mostly conjecture based on scant historical evidence and modern common sense.
Another interesting attribute to the trapezoidal design of these chests and the oddly consistent size of three of the existing examples shows them to be of decent seat height and firmly stackable. So, if we are to believe that these sea chests were for taking on raiding trips, essentially making them campaign furniture similar to a modern soldier’s footlocker, it would indeed be a (lower case) viking chest.
– Kate Fox, excerpt from "Convergent Design: The Six-board Viking Sea Chest" in Issue Five, available here.