rough, energetic, and playful behavior or pranks that could get someone hurt.
From horse (the animal) and play, referring to the rough, boisterous way horses physically interact with each other and their environment. The term emerged in English to describe similarly wild human behavior.
Nobody's really sure why we compare rough play to horses—maybe because horses literally roughhouse and kick, or maybe because horse-training was rowdy work—but the term stuck around because it's perfect for describing pranks that seem funny until someone actually gets hurt.
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