The thong fastening the sandal to the foot; from Anglo-Saxon laeccan, to fasten; from whence comes "latch." To unloose it was a slave's office for a great man (Luke 3:16).
Bibliography Information Fausset, Andrew Robert M.A., D.D., "Definition for 'Latchet' Fausset's Bible Dictionary". bible-history.com - Fausset's; 1878.