An Etymological Dictionary of the German Language/Schnalle

by Friedrich Kluge

Schnalle, f., ‘buckle, clasp,’ from MidHG. snalle, f., ‘buckle,’ shoe-buckle,’ allied to MidHG. snal, m., ‘quick movement’ (for the proper term for buckle see Rinken). Hence the word is probably named from the rapid movement of the spring. See the following word and schnell.