1650s, "snigger," imitative (compare snicker). As imitative of a sound made by a horse, from 1753. As the sound of something beating the air, from 1920. Related: Whickered; whickering.
Entries linking to whicker
snicker v.
"laugh in a half-suppressed way," 1690s, possibly of imitative origin; it is similar to Dutch snikken "to gasp, sob;" also compare the horse's nicker. Related: Snickered; snickering.