From the Internet:
"The Cheval de Frise (horse of Friesland) was the fore-runner of barbed wire entanglements used in warfare. It was a fortification comprised of timber pierced and traversed with wooden spikes pointed with iron five or six feet long and used for stopping a breach, defending a passage or making entrenchments to stop cavalry. They were first used by the Prince of Orange in the siege of Groningen, Friesland in 1594 from whence the name. "