fall asleep

fall asleep idiom
Go to sleep; also, cease paying attention. For example, As soon as the lights were dimmed he fell asleep, or His lectures are so dull that I fall asleep. The literal usage, which uses the verb fall in the sense of “succumb,” dates from about 1300; the figurative is several centuries newer. Also see asleep at the switch.

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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