The English tradition of meat pies dates back to the Middle ages. A typical Elizabethan recipe ran: Shred your meat (mutton or beef) and suet together fine. Season it with cloves, mace, pepper and some saffron, great raisins and prunes..."
The key to dating Shepherd's pie is the introduction (and acceptance) of potatoes in England. Shepherd's Pie, a dish of minced meat (usually lamb, when made with beef it is called "Cottage Pie") topped with mashed potatoes was probably invented sometime in the 18th Century by frugal peasant housewives looking for creative ways to serve leftover meat to their families. It is generally agreed that it originated in the north of England and Scotland where there are large numbers of sheep--hence the name. The actual phrase "Shepherd's Pie" dates back to the 1870s, when mincing machines made the shredding of meat easy and popular."