Malingerer
Malingerer , noun
[French malingre sickly, weakly, prob. from mal ill + Old French heingre, haingre, thin, lean, infirm, from Latin aeger.]
In the army, a soldier who feigns himself sick, or who induces or protracts an illness, in order to avoid doing his duty; hence, in general, one who shirks his duty by pretending illness or inability.