The ancestor from whom this sept take their name is Can / Cahan who appears in the MS1467 MacMillan genealogy asCainn mhic Dubgaill mhic Gillacoluim mhic Gillacrist... Gillamaol. This great-grandson of Gillemaol or Maolan, the eponymous of Clan MacMillan, was one of the leading native nobles in 13th century Galloway, and is on record there in 1273 as Cane Mcgillolane (Mac-Ghille-Fhaolain, from which comes the surname MacLellan - Cahan being an important ancestor of that clan too). His given name is a phonetic form of Cathan and this reflects the fact that the early MacMillans were part of the original Clann Ghille-Chattain. See Graeme M. Mackenzie, "For Ever Unfortunate - The Original Clan Chattan" in Transactions of the Gaelic Society of Inverness, LXI (1998-2000).
Cahan's son Donald was one of the Barons du Realme de Escoce ("Barons of the Kingdom of Scotland") who signed a treaty with king Edward of England in 1289/90. His name is recorded then in Norman-French as Douenald le fit Can (i.e. Dovenald le fitz Can or "Donald the son of Cahan"); but he appears in Barbour's epic account of Robert the Bruce's battles in Galloway simply as Donald McCan. Another prominent son of Can / Cahan was Gilbert the bishop of Man and the Isles who appears in 1328 with the surname MacLellan, but is identified in another reference as the brother of Cutbert M'Cane. A further son, Gibbon fitz Kane, was the eponymous of the MacGibbons, and he's documented in Galloway between 1298 and 1303; while the MacMillans themselves descend from yet another son - who's called Maolmuire mac Cainn in the MS1467 genealogy, but who appears on record in 1263 as Gillemor MacMollan (the Gaelic names Maolmuire and Gillemuire are synonymous).
The surname MacCan(an) appears on mainland Argyll in c.1479 when Duncan Makcane resigned the lands of Crageneure in Glassary, which is just to the north of Knapdale, and in 1539 when the muderers of John Roy MacMillan in Clachbreck, Knapdale, included Suene McKannane, Gilpatrick McKannane, John mc coull vc Kennane (John son of Dugald mhicCannan) and Donald mc ilchallum vc Keynnane (Donald son of Malcolm mhic Cannan) - alongside two MacMillans, one of whom was probably the son of the then clan chief.
The earliest charter connecting Knapdale to a descendant of Gilchrist Gillemaol / Maolan (granted by Edward II of England in 1318) included also the lands of Glendaruel on the Cowal peninsular, and it's there that Clann a' Chainich (or Caniche) had one of their seats - alongside the leading branch of the MacGibbons. John Makane was laird of Kilmun in Glendaruel in 1434, and Ardachearanbeg of Glendaruel (OS Landranger Sheet 55, 002859) was owned in the 1750s by his presumed descendant Duncan M'Channanich of Achatachyranbeg - who also appears as Duncan MacHannanich of Auchtekerrenbeg. The MacChannanichs, along with the MacMillans, the MacGibbons, and other related families, were claimed in the 1720s by William Buchanan of Auchmar as septs of his clan (on the basis of an invented Buchanan ancestor called Methlan and the assertion that "MacMillan" was how MacMethlan sounded in Gaelic). It was apparently as late as 1848 however before the then laird of Achdachiranbeg became Duncan Buchanan, and it's presumed that any descendants he may have had will still be using that name rather than their original surname [Archibald Brown, History of Cowal, 36, 84, 93; Adam, "Clans, Septs...etc. (1970), 575, Appendix V].
In Perthshire and Stirlingshire descendants of Can / Cahan lived alongside the de Lanys or Lennies (who were descended from Cahan's uncle Maoldonich mac Malcolm mhic Mhaolain). A place called Balgibbon can still be found on the other side of Callander from Leny itself, and in 1480 the township of Lundy McCane formed part of the Barony of Doune (the modern farms of Wester, Mid, and East Lundie are north of the town of Doune). There's also a farm called Mackeanston just to the east of the village of Thornhill - not far from the present home of Chief George MacMillan's brother, General Sir John MacMillan. In the 15th century, the Exchequer Rolls show that McKannane had the ferme (lease) of the lands of Drummond before his execution in 1453; and the use of the surname alone suggests that he was the chief of the kindred at this time. In 1480 Donaldo McCane was the tenant of lands in the lordship of Strogartney, which in 1486 he held with his son Fergusio Makane - who from 1488 to 1502 was the sole tenant of the same lands. Cessintuly was also held in 1480 by Donald MacCane - in this case with Thome Baxster and others - and from 1483 he held it with his son Andree McCane. In 1502 father and son were joined in the tenancy of Cessintuly by another Andrew MacCane, one of whom was the sole member of the kindred amongst the tenants there in 1508. Twenty years later Andree Makane had a charter for lands in Cessintuly, and in 1533 he served on an inquest jury regarding the neighbouring lands of Garticaber. This Andrew was probably the father of Donaldo McKane who had sasine in 1537 for the family lands; and who appears again in 1541 when the royal rentals for the barony of Cessintuly note that "Murdestoun and Makanestoun" were "...claimit be Donald McCaane...and produit his faderis charter thairupon." In 1545 however the Queen granted the lands of Cessintulie to James Balfour following their resignation by Donaldus Makane.
In Galloway the early form of the surname was Acannane - from ap Cannain for mac Channain, as with ap Maolagain for mac Maolagain/Mhaolain (for which see Mulligans/Millikens). Though the actual surname does not appear in this area until the 15th century, Can / Cahan's grandson Gilberti Mcgillolane is recorded there during the reign of king David II (1329-71) as the Captain of Clenconnon; i.e. Chief of Clann Channain. In 1477 a Nevin Cannan was granted, along with others, a remission by the crown for the slaughter of Gilbert Rorison; and in 1495 a Thomas Makane appears at Kirkcudbright - along with Johne McMyllane and Colline McMyllane - also in receipt of a royal remission. In 1542 Fergus Acannan is documented as a witness, and in 1553/4 he received a charter from the king for Killauche and other lands in the parish of Balmaclellan (Killochy being just a couple of miles from a place called Ironmacannie - see OS Landranger 77, 649769 and 662757). His great-grandson James Acannane / Cannan appears to be the last of the family to be recorded with the "A" at the beginning of the surname; and his successors can be traced down to a Robert Cannan of Killochie who last appears in 1734. Branches of the Cannan family were also lairds at one time or another of other Galloway properties such as Barlay, Heidmark, Mardroquhat, Barnsalloch, Formonistoun, Fell and Little Knocks, Barlochan, and Kirkennan.
D.V. Cannon & R. C. Reid, "The Cannan Family in Galloway" in TDGNHAS, 3rd Series, Vol. XXXL (1952-3), 78-120.