[go] through the floor

to experience a sudden and significant decline in one's emotional state, confidence, financial situation, etc.

The idiom "go through the floor" is an idiomatic expression that is used to signify a sharp and sudden decrease or decline in something, typically used in the context of prices, values, or performance. Its origin is rooted in the idea of something figuratively falling through the floor or plummeting, much like an object falling to a lower level, representing a substantial drop or decline in a particular aspect.

When the company's financial troubles were revealed, its stock prices went through the floor.
Home prices in the area have gone through the floor due to the economic downturn, making it a buyer's market.
The quality of customer service at that restaurant has gone through the floor in recent months, resulting in a decline in patronage.
As soon as the news broke about the safety concerns, trust in the product went through the floor.
With the unexpected drop in demand, the value of the collectibles market went through the floor, leaving many investors in a precarious position.