A lachet was the thong or fastening used to secure a sandal. Scripture uses the term to express something of little worth and to describe a humble service normally assigned to a servant.
Definition
A lachet was the thong or fastening by which a sandal was attached to the foot.
Biblical Usage
The term is used proverbially for something trivial or worthless. The service of bearing and unfastening the shoes of an important person is presented as work assigned to the meanest slaves.
Historical Background
The lachet belonged to the ordinary fastening of a sandal and was associated with humble service.
Historical Bible Dictionaries
Smith's Bible Dictionary
the thong or fastening by which the sandal was attached to the foot. It occurs int he proverbial expression in (Genesis 14:23) and is there used to denote something trivial or worthless. Another semi-proverbial expression in (Luke 3:16) points to the fact that the office of bearing and unfastening the shoes of great personages fell to the meanest slaves.