When describing a situation that is facing difficulty or deteriorating, it may seem appropriate to use the phrase “fall by the waste side.” After all, waste signifies an unwanted byproduct or the act of diminishing. This word in relation to the phrase, however, is incorrect and often mistaken for the correct word: wayside.
Wayside is a noun meaning “to the side of something” or “landing adjacent to a road or path.” Used in the phrase “by the wayside” (often accompanied by the verb fall), it means a condition of neglect or disuse.
Examples:
1. With negotiations at a standstill, the deal seems to be falling by the wayside.
2. My intention to leave work early has gone by the wayside.
Early usage:
This phrase appeared in the New Testament translation by William Tyndale in 1526 (Luke 8:5).
“A sower went out to sowe his seede: and as he sowed some fell by the waye syde and it was troden vnder fete and the foules of the ayre devoured it vp.”
Source: Christine Ammer, The American Heritage Dictionary of Idioms, (Boston: Houghton Mifflin Harcourt, 2013), 138.