This is the first new word I’ve found in a while that I’d actually use regularly. Malinger: “To feign illness or other incapacity in order to avoid duty or work.”
I can be quite the malingerer. ;) And yes, malingerer really is the noun form of malinger. This word just keeps getting better and better!
It comes from the French word malingrer “to suffer”, and the Online Etymology Dictionary says that the meaning “to feign illness to avoid work” may come from the “notion of beggars with sham sores.”