Lake Hamana was called Totsu-awa-umi as a freshwater sea far away from the capital compared to Lake Biwa, and the names of 'Omi Province (the present-day Shiga Prefecture)' and Totoumi Province (the west of present-day Shizuoka Prefecture) originated from those old lake names.
近淡海に対し、都から遠い淡水の海として浜名湖が遠淡海（とおつあわうみ）と呼ばれ、それぞれが「近江国（おうみのくに、現在の滋賀県）」と遠江国（とおとうみのくに、現在の静岡県西部）の語源になった。