Origin and history of avalanche

"fall or slide of a mass of snow on a mountain slope," 1763, from French avalanche (17c.), from Romansch (Swiss) avalantze "descent," altered (by metathesis of -l- and -v-, probably influenced by Old French avaler "to descend, go down," avalage "descent, waterfall, avalanche") from Savoy dialect lavantse, from Provençal lavanca "avalanche," perhaps from a pre-Latin Alpine language (the suffix -anca suggests Ligurian).

It later was extended to falls of rock and landslides. Shortened form valanche is by 1766. As a verb, from 1872.

Middle English had a verb avalen "to lower (something); come down or descend from a height, flow down," c. 1300, from Old French avaler; with extended senses "yield, give place, let fall, lower, doff" it survived into early Modern English as avale and was used by Shakespeare, Marlowe, Greene, Beaumont & Fletcher.

Also compare archaic valson "a movement downward, descent," used late 15c. in reference to the migration of eels, from Old French avalaison (Latin aualatio).