The Collaborative International Dictionary of English v.0.48:

Latchet \Latch"et\, n. [OE. lachet, from an OF. dialect form of
   F. lacet plaited string, lace dim. of lacs. See Lace.]
   The string that fastens a shoe; a shoestring.
   [1913 Webster]

WordNet (r) 3.0 (2006):

latchet
    n 1: a leather strap or thong used to attach a sandal or shoe to
         the foot

Easton's 1897 Bible Dictionary:

Latchet
   a thong (Acts 22:25), cord, or strap fastening the sandal on the
   foot (Isa. 5:27; Mark 1:7; Luke 3:16).