What is "pierres"

There are works that are named Pierres, pronounced like Pierre:

• Pierres (novel), a novel of Victor Hugo
• Pierres (poems), a collection of poems of Roger Caillois

Pierres is the name of several communes in France:

• Pierres, Calvados, in the Calvados département
• Pierres, Eure-et-Loir, in the Eure-et-Loir département