Also, dead tired. Extremely weary, as in Mom was in the kitchen all day and was dead on her feet, or I'd love to go, but I'm dead tired. The use of dead for “tired to exhaustion” dates from the early 1800s, and dead on one's feet, conjuring up the image of a dead person still standing up, dates from the late 1800s.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.