The surname of McKINLEY was originally derived from the Gaelic Mac Fhionnlaoich a name meaning 'fair-hero'. The name is distinctively a Scottish one, but is found also in the north of Ireland (Antrim) among the descendants of the Scots Plantation of Ulster. Scottish surnames fall into two quite distinct groups; those of Gaelic origin and those of English origin. The Gaelic language was brought to Scotland from Ireland around the 5th century AD, displacing the British language (an early form of Welsh) previously spoken there as well as elsewhere. Gaelic was the main language of that part of Scotland not subject to English influence, a rather more extensive area than the present day Highlands and Islands, where Gaelic is still spoken in places. It is from these northwestern and western area of Scotland that surnames of Gaelic origin, now almost universally Anglicized in form, have been disseminated around the world. Early records of the name in Scotland mention Gilaspyh M'Kinley, who witnessed a charter to Archibald, earl of Argyll in 1493. Malcolm M'Inley was denounced as a rebel in Balliwilling in 1675. William McKinley was twenty-fifth president of the United States (1897). The first people in Scotland to acquire fixed surnames were the nobles and great landowners, who called themselves, or were called by others, after the lands they possessed. Surnames originating in this way are known as territorial. Formerly lords of baronies and regalities and farmers were inclined to magnify their importance and to sign letters and documents with the names of their baronies and farms instead of their Christian names and surnames. The abuse of this style of speech and writing was carried so far that an Act was passed in the Scots parliament in 1672 forbidding the practice and declaring that it was allowed only to noblemen and bishops to subscribe by their titles. In the Middle Ages heraldry came into use as a practical matter. It originated in the devices used to distinguish the armoured warriors in tournament and war, and was also placed on seals as marks of identity. As far as records show, true heraldry began in the middle of the 12th century, and appeared almost simultaneously in several countries of Western Europe.
McKinley is a Scottish-Irish surname historically associated with northwestern Ireland's former Kingdom of Tir Chonaill, northeastern Ireland's former Ulidia (kingdom) and the Highlands of Scotland or the lands of today's Donegal, today's (in modern usage) Ulster, and the Scottish Highlands. The McKinley are of the ancient Ulaid race and are a branch of its MacDunleavy (dynasty) royals (original Gaelic language Mac Duinnshléibhe) of Ulidia kingdom. Two etymologies are proposed for the origin of the surname McKinley. The surname, like that of the McClay and the Clan MacLea, is an Anglicization of a Scottish-Gaelic slurring of the Irish-Gaelic Mac or Ó Duinnshléibhe. A second entomology proposes that the Anglicized surname McKinley, like the surname MacNulty (Gaelic language Mac an Ultaigh, trans. "of Ulidia"), arose originally from a Gaelic language nickname given the deposed MacDunleavy dynasty royals while exiled in Tirconnell and elsewhere. Being, also, one of Ireland's ancient hereditary medical families, the MacDunleavy (variant English spelling MacDonlevy) were in Tir accorded the high Gaelic status of "ollahm leighis" or the official physicians to the O'Donnell dynasty kings of Tyrconnell and practiced as physicians while exiled in Scotland. The nickname was Mac in Leigh. Per this scenario the Gaelic language patronymic forming prefix "Mac" (meaning "descended of") is joined to the Gaelic language "Léigh" meaning leech, but denoting a physician. Leeching (medical) having been for millennia, in Gaelic Ireland and elsewhere, a commonly employed medical practice. Scholars, adhering to either proposed etymology for McKinley, equate the McKinley with the MacNulty as MacDonlevy. Wiki, McKinley surname