|Kanji in this term|
The name is a description of the mirror's size. A circle with a diameter of one 尺 (shaku, ancient foot, unit of length) would have a circumference of four ata. A circumference of eight ata would thus mean a mirror with a diameter of two shaku. The shaku at that time was roughly 23 centimeters, so the mirror would have been roughly 46 centimeters across.
- The ata of that time period was around 18 centimeters or 7.25 inches, so note that the hand in the English name is not the same as the four-inch unit of measurement.