A backlash is a strong hostile reaction to a change. A public backlash, face a backlash, backlash against the policy.
It nearly always takes against and implies the reaction was larger than anybody expected. The literal sense is mechanical: backlash is the slack in a gear train that lets a wheel move before the next one does.
1nounbacklashA strong hostile reaction to a change.
“The plan to close the library caused a huge backlash from local parents.”
backlash is a reaction.
Back plus lash, from the mechanical sense of a sudden reverse movement.
Middle English
bak
English
back
English, today
backlash
From back- + lash. back comes from Middle English bak. From Middle English bak, from Old English bæc, from Proto-West Germanic bak, from Proto-Germanic baką, possibly from Proto-Indo-European bʰeg- (“to bend”). The adverb represents an aphetic form of aback. Compare Middle Low German bak (“back”), from Old Saxon bak, and West Frisian bekling (“chair back”), Old High German bah, Swedish - and Norwegian bak. Cognate with German Bache (“sow [adult female hog]”).
Etymology from Wiktionary, CC BY-SA