The Collaborative International Dictionary of English v.0.48:

Sob \Sob\, v. i. [imp. & p. p. Sobbed (s[o^]bd); p. pr. & vb.
   n. Sobbing.] [OE. sobben; akin to AS. se['o]fian,
   si['o]fian, to complain, bewail, se['o]fung, si['o]fung,
   sobbing, lamentation; cf. OHG. s[=u]ft[=o]n, s[=u]ftj[=o]n,
   to sigh, MHG. siuften, siufzen, G. seufzen, MHG. s[=u]ft a
   sigh, properly, a drawing in of breath, from s[=u]fen to
   drink, OHG. s[=u]fan. Cf. Sup.]
   To sigh with a sudden heaving of the breast, or with a kind
   of convulsive motion; to sigh with tears, and with a
   convulsive drawing in of the breath.
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         Sobbing is the same thing [as sighing], stronger.
                                                  --Bacon.
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         She sighed, she sobbed, and, furious with despair.
         She rent her garments, and she tore her hair. --Dryden.
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