Comment by pjmlp

I used a more recent term known to Web developers.

It means going through the image and remove most code that isn't directly needed by the application, or only exists to support developer workflows.

Usually needs a bit help for fine tuning, regarding what code to keep, and what to delete.

You also find this on Java (jlink, ProGuard, D8/R8 on Android), and .NET (trimming, .NET Native manifests).