Back Up The Truck

What Does Back Up The Truck Mean?
Slang that refers to the purchase of a large position in a stock or other financial asset by an investor or trader. Typically, when someone is willing to back up the truck on a financial asset, this implies that they're extremely bullish on that asset's performance.

Investopedia explains Back Up The Truck
For example, if an analyst recommends that it is time to start backing up the truck on XYZ stock, this means that he or she is extremely confident and upbeat about how well XYZ stock will be doing in the foreseeable future.

The term refers to the imagery derived from a truck backing up to a warehouse or some other commercial building to load up goods.