Is it a classic mistake Ludwig. The last bit “fest” is short for festival. The rock group Wisbone Ash used to have a weekend music event featuring concerts and chances to meet the band etc. The weekend was known as Ashfest and has run for many years. There many other such “xxxfest” events.
Gaulfest originally was held in the Welsh Borders so hills in UK regions G/WB, GW/NW and GW/MW were the intended targets back nearly 20 years ago. In a light-hearted manner the name was meant to be derived from the ancient name for Wales: “Pays de Galles”. But in error, instead of it being Gallesfest it was written as Gaulfest. That name has been used for many such mass activations.
Originally there would have been mainly 2m SSB/FM operation as SOTA was UK and EI only then. Now you can take part no matter where in the world you are located as many of the stations in the original regions will be QRV on HF as well.