The association of clans with disorder is in part due to their turbulent origins. A number of races converged on Scotland, leading to conflicts over cultural and ethnic differences. For instance, the MacLeods derive from Norsemen; the Murrays and Sutherlands from Flemish stock; the Bruces and Frasers from Normans and Angevins; the royal Stuarts from a Breton nobleman; Clan Chattan from Celts. As Scottish culture developed into greater hegemony, many of these feuds subsided.
Feuds often developed between neighboring clans in the form of territorial disputes. Religion, politics, and even unrequited love have all contributed to feuding.
Two clans that the Keiths often found themselves in contention with were the Gunns and the Irvines.
In the fourteenth century by a marriage with the heiress of the Cheynes of Ackergill, the Keiths took possession of lands in Caithness, and for a long time their settlement there was a source of feuds with the Clan Gunn. For greater detail into this historic feud between the Keiths and Gunns, read Ned Buxton's article in Keith & Kin.
The following account, entitled "The Crowner Slain by the Keiths in the Chapel of St. Tayre", comes from a 1764 text:
About the year of God 1478, there was some dissention in Caithness betwixt the Keiths and the Clan Gunn. A meeting was appointed for their reconciliation, at the Chapel of St. Tayre, in Caithness, hard by Girnigo, with twelve horse on either side. The Crowner (chieftain of Clan Gunn) with the most part of his sons and chief kinsmen came to the chapel, to the number of twelve; and, as they were within the chapel at their prayers, the Laird of Inverugie and Ackergill arrived there with twelve horse, and two men upon every horse; thinking it no breach of trust to come with twenty-four men, seeing they had but twelve horses as was appointed.
So the twenty-four gentlemen rushed in at the door of the chapel, and invaded the Crowner and his company unawares; who, nevertheless, made great resistance. In the end the Clan Gunn were all slain, with the most of the Keiths. Their blood may be seen to this day  upon the walls within the Chapel at St. Tyre, where they were slain. Afterwards William Mackames (the Crowner's grandchild) in revenge of his grandfather, killed George Keith of Ackergill and his son, with ten of their men, at Drummuie in Sutherland, as they were travelling from Inverugie into Caithness.
Source: The History of the Feuds and Conflicts Among the Clans in the Northern Parts of Scotland and in the Western Isles: from the year M.XX1 unto M.B.C.XIX, now first published from a manuscript wrote in the reign of King James VI
Both families originated in the North-east and got their lands from King Robert the Bruce. He granted both the Irvines and the Keiths land and hereditary honours for their loyalty during the Wars of Independence, such as in the years which followed the Battle of Bannockburn in 1314. Sir William Keith owned land around Kintore and Inverurie but added estates in Kincardine, on the south bank of the River Dee, through marriage. This brought the Keiths and the Irvines, who owned the land on the north bank of the Dee, face to face, After a time there was prolonged skirmishing across the Dee and this culminated in a battle at Keith's Muir on the north side of the river at Drumoak. None of the invading Keiths was left to tell the tale. The feud was eventually settled and the families reconciled by marriage.
From Keith & Kin, Third Quarter 2002
A feud which goes back 600 years was finally consigned to history over the weekend when two North-east clans came together for a landmark gathering, Members of the neighboring clans Irvine and Keith met at Park Bridge of Drumoak to reinforce their friendly relations. Let by a piper and a pipe band respectively, the families gathered near the site where the Irvines massacred a number of Keiths in the early 1400s. Read the entire article about the peace agreement between Clan Keith and Clan Irvine