2001, Michael B. Arthur, Denise M. Rousseau, The Boundaryless Career: A New Employment Principle for a New Organizational Era, Oxford University Press (→ISBN), page 140:
Everybody knows that when you have a layoff, you use it as chance to get rid of the people you wanted to get rid of anyway, but couldn't document or hadn't bothered documenting as bad employees […]. If you don't have much dead wood, you hope they make you use a seniority list, because then you can say it's out of your control.
Used other than figuratively or idiomatically: seedead, wood.