Fallen out of use, discarded. This expression usually is put as go by the board, as in With all the crime around here, the practice of leaving the house unlocked has gone by the board. The board here is the board of a ship, and the expression has been used since about 1630 to signify something that has fallen overboard and been carried away. [Mid-1800s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.