The name is a little bit misleading in English, as in Dutch the event is known as the "Hoekse en Kabeljauwse Twiste" or the Conflict between the Hooks and the Cods. It's not a war between literal hooks and cods, but between two factions in the County of Holland, the "Kabeljauwen" or Cods, and the "Hoeken" or Hooks.

As for the origin of this conflict, a problem arose after the death of the Count of Holland, Willem IV. He died in 1345 during the Battle of Stavoren and was childless, so the County came into the hands of his sister, Margaretha II van Henegouwen, who was also the wife of the Holy Roman Emperor, Lodewijk de Beier. Margaretha's son, Willem V, was the legal heir of the County of Holland but was at this time too young to rule, so she and her uncle, the younger brother of Willem IV, ruled in his stead.

During the rule of Willem IV the cities of the County of Holland had been taxed dearly to pay for all of the battles and wars of their Count, which had lead to considerable turmoil and unrest. Also under Willem IV, nobles had been able to buy positions in the court of the Count. When Willem IV died, nobles who hadn't bought their position yet feared that they'd be unable to do so under their new rulers, which would put them at severe disadvantage when it came to claiming important positions and the pay that was bound to them.

Then in 1349, Willem V was finally old enough to assume direct rulership of the County. But in the past few years Margaretha and her uncle had been unable to appease either the cityfolk or the nobility. And to make matters worse, the plague was making its way through the Low Countries. The economy was at an all-time low. So when cityfolk and nobles heard that the accession of their new Count was paired with the hefty upfront sum of 15000 Guilders and that there was also a yearly payment of 6000 Guilders to the new Count, they were, to put it bluntly, rightfully pissed off.

Nobility and cities alike refused to pay these sums to their new Count when they came together in 1349. A couple of nobles saw only one option, a revolt! They would fight against Margaretha, her uncle and her son and force Willem V to give in and become their Count without paying the upfront and annual payments.

And how did this alliance of nobles call themselves? The Kabeljauwen, or Cods, of course! Some say the name comes from the coat of arms of the house of Beieren, whose blue and white pattern is reminiscent of the scales of a fish. Others say that the name comes from the fact that cods eat a lot, and as they do so they grow stronger and eat even more. Kinda akin to how the Kabeljauwen thought their alliance would grow and become stronger and grow more.

Now a counter alliance was quickly formed by nobles and cities who instead supported Margaretha and the new Count, Willem V. And how do you catch a fish? With a hook! So they called themselves the Hoeken, or Hooks, ready to catch those revolting Cods and reel them back in!

Now this conflict would go on for a very long time, from 1350 to 1490, with long stretches of peace. Yet even then society would still be divided amongst Hooks and Cods. The allegiance of regions, cities and nobles would change over time, as did the goals of the two factions. For example, after the death of Willem VI in 1417 the conflict became more about pro-Burgundians, the Kabeljauwen, versus anti-Burgundians, the Hoeken. And by 1481 the conflict had expanded from the County of Holland and County of Zeeland to the Prince-Bishopric of Utrecht. By 1490 the Hoeken were finally defeated by the Kabeljauwen, although by that time the conflict had moved to those supporting Maximilaan I van Oostenrijk becoming ruler of the Low Countries, the Kabeljauwen, and those opposing his rule, the Hoeken.