sough definition by Webster's New World
Origin: 19th circa ; from Northern dialect, dialectal ; from Middle English swough ; from Old English swogan, to sound ; from uncertain or unknown; perhaps Indo-European base an unverified form (s)waĝh-: see echo
Origin: ME swowen, soghen < OE swogan, to sound
sough definition by American Heritage Dictionary
intransitive verb soughed, sough·ing, soughs
Origin: Middle English swowen, soughen, from Old English swōgan.