The word a (also aa), used as a hydronym. From Proto-Germanic *ahwō (“waters, river”), from Proto-Indo-European *h₂ekʷeh₂ (“water”); both natively, and through Dutch Low Saxon Aa and German Low German Aa (both from Old Saxon aha (“stream”)), and German Aa (from Old High German aha (“stream”)). For more information, see a and its cognate English ea.