When it comes to St. Paddy's Day, many people imagine they have an Irish grandmother… and perhaps in part they do.

If someone asked you what the names Finbarr Mullaney, Aidan O'Malley and Deirdre McGoldrick have in common your answer might be "Irish." But what if the three people were named Boudreau, Creaser and MacIsaac? No visions of shamrocks and leprechauns dancing in your head? We attribute ethnicity by family name, but the latter group could be Irish through their mothers.

Genealogists learn that few of us are thoroughbreds. When people write about an ethnic group, they may be casting the net more widely than it seems. In the case of the Irish it soon becomes evident that they were good mixers in matrimonial terms. It sometimes appears, especially in March, that everyone has an Irish grandmother. It's certainly true that a great number of us owe some of our genes to an ancestor who came from the Emerald Isle.

Irish people turn up everywhere. The Acadian Caissy family name (and other spellings) began as Casey. There were Irish in Louisbourg. The first Anglican bishop in the Atlantic Provinces was born in County Donegal. My late father once joked that "Julius Caesar had an Irish wife because when he came to the Rubicon he said to 'Bridget.'"

At one time there were so many Irishmen in the British army that a regiment without a Murphy was rare. One historian observed that, between 1689 and 1789, nearly half a million men born in Ireland, their sons or grandsons, wore the uniform of the French army or navy.

It's generally believed that the Great Irish Famine of the late 1840s is what brought the Irish to these shores. However, except for the influx in the vicinity of Saint John, NB, in 1846-1849, most of the Irish families in Newfoundland, Nova Scotia and Prince Edward Island were already here before the Great Famine, as were the majority of Irish settlers along the Gulf coast of New Brunswick.

When you look at historical records you might form a kaleidoscopic view of an ethnic group: here was a shipment of convicts transported for several years-or for life-for offences as petty as stealing a handkerchief. There were the survivors of a shipwreck who made it to shore. Another group arrived just after an Irish rebellion and were questioned by local authorities seeking to discover fleeing rebels.

Small family groups arrived here, perhaps part of a pattern of migration between the home community and the new. Some lived in Newfoundland working in the fishery for a few years or many, then moved on to the mainland. Halifax and Saint John were a stopover for those who couldn't afford the fare all the way to New York or Philadelphia. Work on the Shubenacadie Canal or in the timber woods kept some here long enough that they never left.

The Irish who came here proved to be a law-abiding bunch for the most part, except for when some demagogue or rabble-rouser stirred up sentiment against them. There were riots and nasty moments, but overall the adjustment was gradual and smooth. They sent money home to support the movement to repeal the union of Ireland with Britain and, fortunately for genealogists, newspapers of the day published lists of the supporters, often telling a person's place of origin in Ireland.

In the days before photography, the army kept detailed records of its soldiers in "depot description books." If a man was killed in action or "ran" (went AWOL), the depot book gave his physical description, his trade, and said where he came from. When I combed those books for several regiments and compared the names to pension records and land grants, I found it to be an unquarried goldmine.

In fact over the years I've collected names and places of origin of many Irish, orange or green, who reached these shores. Inspired by the work done in the US in this regard, I gathered my findings into a book, Erin's Sons: Irish Arrivals in Atlantic Canada 1761-1853. Perhaps you will find a nugget in your shovel if you quarry the book-whether you think you're Irish or not.

Dr. Terrence M. Punch is the author of Erin's Sons: Irish Arrivals in Atlantic Canada 1761-1853 (Baltimore: Genealogical Publishing Company, 2008).