From WikiTemp, the GBAtemp wiki
The name GBAtemp has stuck with the site since it's beginnings in 2002. It is composed of two parts; GBA of course stands for Game Boy Advance. The temp is short for temporary. At the time of the website opening it was a ROM site and provided downloads to the latest 10 GBA releases. As ROM sites usually had a very small life expectancy before they ran into legal trouble and were shut down the website was therefore designed as a 'temporary' ROM site. Hence "GBAtemp".
Although the focus of the website is no longer primarily on GBA but instead Nintendo DS and Wii, site staff have remained adamant about changing the name of the website. The name GBAtemp reflects the website's identity and humble beginnings. There will never be a name change.