Even the lowliest will sometimes come to the fore, as in They may not listen to me now, but just wait, every dog has its day. This proverbial saying alludes to the lowly status dogs once held. [Mid-1500s] Also see had its day.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.