sough (sou, sŭf) intr.v.
soughed, sough·ing, soughs To make a soft murmuring or rustling sound. n. A soft murmuring or rustling sound, as of the wind or a gentle surf.
[Middle English swowen, soughen, from Old English swōgan.]
"to make a moaning or murmuring sound," O.E. swogan, from P.Gmc. *swoganan (cf. O.S. swogan "to rustle," Goth. gaswogjan "to sigh"), from PIE imitative base *(s)wagh- (cf. Gk. echo). The noun is c.1381, from the verb.