some info: when people think about a "goedendag", they think about Flemish peasants who are waving around a stick, where a metal bol is attached to with sharp points. Such a weapon wouldn't have had much effect on the battlefield.
The real "goedendag" was an instrument that was tacticaly far more usefull to cause damage. It was a firm long stick with a metal iron point at the end: it was both a weapon to hit with as to stab with, used to knock out horses aswell as the riders. With their pikes & "goedendags", the flemish ranks formed a strong wall.
The flemish city militia, who fought against the French Army at the famous "Guldensporenslag" in 1302, where definetly not inexperienced boys. They were good, trained units: the armed forces of, what were at the time, the mightiest cities of Western-Europe.
Origin of the name"Goedendag":
Nobody really knows, there are a lot of theories. But here's the best one: the weapon was used to stab the throuth of the enemy. this caused the head of the enemy to knod/fall forward, as if he was saying "good day"