The story
- Proto-Indo-European · derived from*el-“to flow”
- Proto-Celtic · derived from*aleti“to grow, nourish”
- English todayAlaunus
From Celtic/Gaulish name, possibly from Proto-Celtic *aleti (“to grow, nourish”). Or, possibly from Proto-Indo-European *el- (“to flow”); in either case, related to the city Altinum in Venetia.
Etymology from Wiktionary, CC BY-SA 4.0.