There isn't a single, widely accepted nickname for sedimentary rocks. Unlike igneous rocks, which are sometimes nicknamed "fire rocks," sedimentary rocks don't have a common nickname.

However, you could use some descriptive terms to refer to them informally:

* Layered rocks: This emphasizes their characteristic formation in layers.

* Fossil rocks: Many sedimentary rocks contain fossils, making this a descriptive nickname.

* Earth history rocks: Sedimentary rocks provide valuable clues about the Earth's past.

Ultimately, the best nickname depends on the specific context and the type of sedimentary rock you're referring to.