For Those About to Rock…
You might like a drink on the rocks if your relationship is on the rocks. In the first idiom, rocks just mean ice. The latter originally refers to a ship in dire trouble because it has run into rocks which are breaking it apart, a particular danger when most ships were made of wood.
Something essential is often called a “cornerstone” because the stone in the corner of a building, where two walls begin from, was traditionally a first and foundational part of the structure. Since they are often laid in a ceremony to mark the start of construction, cornerstones frequently have dates or other inscriptions on them, and some are hollow and filled with items like a time capsule.
The first person to think that they just passed a major milestone was likely traveling the Appian Way near Rome about 2,300 years ago. This remarkable road – still usable today – was the first to use stones as inscribed distance markers. Modern travelers may navigate with GPS rather than stones, but the term “milestone” remains for markers on this road that is life.