Limestone got its name because it is primarily made up of calcium carbonate (CaCO3). This compound is commonly found in the form of limestone, which is a sedimentary rock.

Here's a breakdown of how the name came about:

* Lime: The term "lime" comes from the old English word "lim," which referred to a white, sticky substance. This substance was made by burning limestone to produce calcium oxide (CaO), also known as quicklime. Quicklime was used extensively in construction and agriculture.

* Stone: This simply refers to the fact that limestone is a solid rock.

Therefore, the combination of "lime" (referring to its chemical composition) and "stone" (referring to its form) led to the name "limestone."