From Middle English forswunken, past participle of forswinken (“to overwork”), equivalent to for- + swunk. More at forswink.
forswunk (not comparable)
- (obsolete) totally worn out of work
- 1943, "Just Another Word: Comprising A Word in Your Ear & Just Another Word", Ivor John Carnegie Brown, Ivor Brown, p. 112
- If indeed he had so turned from Latin texts to garden-tools, he would certainly have been forswunk.