the part of a person's foot between the ball and the ankle 脚背;足弓 ■the part of a shoe which fits over or under this part of a foot 鞋面;足弓部鞋底 ■a thing shaped like the inner arch of a foot 形似内足弓的物件
语源
late Middle English: of unknown origin; compare with West Frisian ynstap 'opening in a shoe for insertion of the foot'