The earliest reference I can find is the 1955 Worldcon publications, but my research is not exhaustive and I'm not an expert on this. The 1953 Worldcon just called them "Achievement Awards," apparently (going by their publications). There were no awards in 1954.

All in all, it's starting to look like the 1955 Worldcon was where the Hugo Awards reached more of their now-familiar form, with the 1953 Awards being more of a prototype for what would follow.