It’s a Germanic word, based on the idea of an unmeasured amount of something, haphazardly put together.  Lumpe is a Norwegian and Swedish kind of cake, mentioned by the OED in the entry under “lump”.  I’m not sure what to make of that – would any Word Fans care to post a recipe for lumpe?

• 06.040 then lumps of rock were disturbed

“lump, n.1.” OED Online. Oxford University Press, June 2015. Web. 29 July 2015.