“Go haywire” began as a literal expression in the American West. Hay wire was wire used for baling hay, and when it was unspooled carelessly, it could kink, twist, and tangle badly. That messy, unmanageable state gave rise to the phrase.
By the early 1900s, English speakers were using go haywire figuratively. Instead of talking about actual wire, they used it for anything that started to behave unpredictably or fall apart.
- For plans or situations: “Our schedule went haywire after the storm.”
- For machines or systems: “The printer went haywire during the update.”
The phrase usually suggests confusion, loss of control, or a sudden breakdown in order. It is informal, vivid, and still very common in everyday English. Even though most people are not thinking about baling wire when they say it, the image of something getting twisted and hard to manage still fits the modern meaning well.