clock in

clock in idiom
Begin work, as in She clocked in late again. Also, clock out, end work, as in Please wait for me; I forgot to clock out. The allusion here is to punching a time clock, a device that punches the time on a card to record when an employee arrives and departs. [Late 1800s]

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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