The Saxon fighting knife.
The earliest known Scandinavian Saex dates about 300B.C. with the design and style about the same only and size mainly changed such as the Langsaex (30in.) to the average size of ( 6in.)  called Handsaex.
Many people classify this as a fighting knife. Odd, is it not, that we think of a “Fighting knife” as a small folding knife with a plastic handle and a Tanto blade?
But if you lived in the 5th century and you were of Saxon/Viking Bloodline you would have something like this:
The blade made of iron a handle made of wood or bone no hand guard and with a thick wide edge for strength when chopping and cutting. Even as the saex was very popular it was entirely a matter of preference in the Icelandic “Saga of Weapons Fjord,” the warrior Geitir observes that “he with a little sax must try and try againâ€.
By the 11th to 13th century the Rondel dagger was becoming a common dagger to carry and was extremely ornate and fashionable to carry as you see in many Renaissance works of Art. Both clothes and weapons became more fashionable as the times changed, the battlefield changed, and the clothes changed.
Maybe it has something to do with the clothes we wear that determines the weapons we carry.