sandal

Definition:

A sandal is a simple flat-soled shoe held onto the foot by straps that go around the foot or ankle. Sandals are worn by both men and women.

A sandal was sometimes used to confirm a legal transaction, such as the selling of property: one man would take off a sandal and give it to the other.
Removing one's shoes or sandals was also a sign of respect and reverence, especially in God's presence.
John said that he was not worthy to even untie Jesus' sandals, which would have been the task of a lowly servant or slave.