For may years I heard the "3 brothers" story in my own family, complete with the references to: a) La Rochelle, b) timing in relation to the revocation of the Edict of Nantes, c) an original spelling of "medille" or something along those lines.I think much of this was advanced by an Olive Madill (a Madill researcher) in the 1960s, though the persistence of this tale (?) would suggest an origin well before then.
I too long subscribed to this family origin, and while it's entertaining, there seems to be a distinct lack of evidence to support such a history.Certainly there has been no conclusive proof of French origin, only anecdotal.
Over the years, I have collected the following points AGAINST the 3 brothers/Huguenot/French theory and FOR a Scottish origin. In no particular order:
1) The "x brothers" theme is remarkably common; the Madills do not have a lock on this. While such familial migrations certainly occurred (it's well documented for Madills from Monaghan moving to Canada!), it is also apparently one of the most common mis-leading oral traditions in many families. Look over the FAQ section of any major genealogy website and you'll probably find cautions on accepting such stories outright.
2) In modern French, the English "male" is rendered "mâle" (the accent over the "a" being the figure commonly over the '6' key on the English/American keyboard). French pronunciation of this word doesn't get close to "Madill" at all. Others have suggested Madill originated as the French word for metal and/or metal-worker; again, the modern French pronunciations offer no hint of modern Ulster pronunciation of the name Madill.
3) Research of books on French surnames reveals NOTHING even plausibly close to the present-day Madill, and stunningly little that evens starts with "m", followed by any vowel, then "d". There ARE, however, a good number of modern "Irish" surnames with well-documented links to their original FRENCH version (fellow Madill researcher Mr Corbett bears such a name); why wouldn't Madill appear in such studies?
4) The Huguenot Society, noted as thorough recorders and researchers of the movement of persecuted French Christians, have NO records supporting such a family name.
5) The book "Surnames of Scotland" by (Fraser?) Black contains entries for MCDILL and MCDOWELL that offer strong support for the existence of the name, or at least the SOUND (spelled variously) long before the Huguenots started fleeing France. A major university library will have this in its holdings. This book is the single strongest hard evidence of the presence of the name in Ulster before 1685. The key points in Black's book are: a) traditional Scottish names beginning with "MC" or "MAC" were routinely mangled in the recording. b) Mc/Mac names were often written using an apostrophe in lieu of the Mc/Mac ... M'Dill / M'Dull (spelled just that way) were noted in records in the late 1500s/early 1600s. An amazing variety of spellings -- all of which SOUND like MADILL -- are cited in the book with specific date and document references. c) spelling was not as relevant as SOUND. Literacy wasn't as widespread as we family historians would have wished! The cleric or town official who recorded a major life event rendered the name as he HEARD it, hence Madole, Maduel, Maddol, Madill, Medill, all being found in modern (1800s+) records. This is not to mention the variants which actually used a "c" somewhere in the spelling.
6) The name MCDOWELL is VERY common (today and historically) in those parts of Scotland located nearest the Antrim coast. Migration of MCDOWELL'S to/from Antrim and Down was therefore highly likely; remember, it's less than 15 (sea) miles from Fair Head in Antrim to the Scottish coast ... a much shorter distance to migrate than from Brittany.
7) Scots and Ulsterman even today (even some in my own family) can pronounce "MCDOWELL" in a fashion that you'd be inclined to spell as Madell, emphasis on the "dell" with little or no hint of the "c".
8) There are documented records of Madill families (all from Antrim as far as I know, but why would this differ for Monaghan?) wherein individual members of the SAME family (siblings!) spelled their name as either MADILL or MCDILL. This also occurs in Madill/McDill immigrants to the U.S. Alternatively, in the Mormon records you can find the birth of three children (in either Ulster or Scotland) of the SAME couple with the surname spelled first MADILL, second MCDILL, and third MEDILL. Again, this suggests connection with a Scots origin.
9) Madills in County Antrim (my family) have a well documented link of movement back and forth between Antrim and the Glasgow area. Some families would have children in both locales, suggesting a strong base of Madill/McDill families in Scotland. When would THEY have migrated from France?
10) The "Huguenot" aspect of the tale is NOT baseless. The Crown garrisoned troops in northern Ireland immediately after the late 1600s (Battle of Boyne, etc) ... how else to keep hard-won territory under control? Among those troops considered most loyal to William would have been Scottish troops -- Calvinist in faith and geographically handy. It was also not unusual for such forces to be commanded by dislocated FRENCH (Huguenot) officers, skilled in military matters, reliable in faith, but not welcome in France. William of Orange's forces contained such (mercenary officer) individuals. By extension it is entirely believable that MCDOWELLs (soldiers from reliable Scottish units from nearby Dumfrieshire, Scotland) could have arrived in northern Ireland WITH French Huguenots; it just doesn't seem as plausible they these MADILL forerunners were themselves Huguenots.