The name came from people looking through their legs from Kasamatsu Park on the north side, a view that is traditionally considered very beautiful (the view from Kasamatsu Park is also called a "slanted number 1").
北側の傘松公園から「股のぞき」で見るのが名称の由来でもあり、伝統的に美しいとされている（この傘松公園からの眺望は、「斜め一文字」とも呼ばれる）。