Also, for one's life. Desperately, urgently, so as to save one's life. For example, When the boat capsized, I hung on for dear life, or With the dogs chasing them they ran for their lives, or She wanted that vase but I saw it first and hung on to it for dear life. These expressions are sometimes hyperbolic (that is, one's life may not actually be in danger). The first dates from the mid-1800s, the variant from the first half of the 1600s. Also see for the life of one.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.