note: all three forms are in use but deathbed seems to be preferred.
From Middle English dethbed, from Old English dēaþbed, dēaþbedd (“deathbed; grave”), equivalent to death + bed. Cognate with Swedish dödsbädd (“deathbed”). Compare also Dutch sterfbed (“deathbed”), German Sterbebett and Totenbett (both “deathbed”), Danish dødsleje (“deathbed”).
deathbed (plural deathbeds)