sarsen (n.) Look up sarsen at
"large sandstone boulder," 1640s, properly sarsen stone, i.e. "Saracen stone," from Saracen in the old sense of "pagan, heathen." The same word was applied to the ancient leavings outside Cornish tin mines, also known as Jews' pits, those being the terms that came to mind once to describe any ancient features, based on the Bible.