 The name is often shortened to Mt Joy, as in Mencken (1963).However, citizens of the town often point out that this abbreviation is not proper because the town is not named for a mountain but is named after the "Good Ship" Mountjoy which famously broke a Catholic siege during the Siege of Derry.Due to the early settlement of the Protestant Scots-Irish in this region of Pennsylvania, many of the municipalities in the area were given names common to the North of Ireland such as