We encountered Kummer (sorrow, grief, anxiety) already in Liebeskummer, our word of the month for December 2009. Speck is the fatty tissue people or animals may carry on their bodies.*
Kummerspeck, then, is the stuff that grows visibly around the midriff of people who overeat out of anxiety or grief.
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*It may be also a byproduct of the slaughtering of hogs, eaten as such or used to flavor dishes; but that's not the meaning in the present context.
Evolutionary semantics
1 hour ago