mid-15c., "defending, act of protecting or keeping (something) in proper condition" (short for defencing); 1580s in the sense "art of using a sword or foil in attack and defense" (also fence-play); verbal noun from fence (v.). Meaning "putting up of fences" is from 1620s; that of "an enclosure" is from 1580s; meaning "receiving stolen goods" is from 1851 (see fence (n.)); meaning "materials for an enclosure" is from 1856.
Despite the re-enactment in 1285 of the Assize of Arms of 1181, fencing was regarded as unlawful in England. The keeping of fencing schools was forbidden in the City of London, "as fools who delight in mischief do learn to fence with buckler, and thereby are encouraged in their follies."[fencing etymology, fencing origin, 英语词源]