Duplisea Duplessis and Sirois Genealogy by Mark S Duplisea 

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The true surname of Francois SIROIS dit DUPLESSIS was SIROIS. "Dit" in French means "say" and in this context, it means "called." In this instance: Francois SIROIS called DUPLESSIS.  At some point one of Francois’ ancestors who was named SIROIS took on DUPLESSIS as a “dit” name. Francois’ father was Jean SIROIS dit DUPLESSIS. Since it appears Jean never came to America, DUPLESSIS must have been added in France.

The addition of a “dit” name was very common. 

In any case, very often the dit name was passed down to later generations, either in place of the original surname, or in addition to it. Some of his children might then keep the original surname, and some might use the dit name. After a few generations, it's not uncommon to completely lose the memory of the original name, or to forget which was the original and which was the dit name. Besides Sirois dit Duplessis, here are a few other common “dit” names from the lower St Lawrence river valley.

In each case the original family surname (i.e. Roy) has a name added (i.e. Desjardins). 

The meaning of Sirois is not certain, possibilities include:

 The meaning of "DuPlessis" is of or from "Plessis" where "Plessis" is a place name. In France "plessis" were fortified mounds built as strongholds on top of cliffs.  Many small places came to be known as "Plessis".

The first few generations of descendants of Francois SIROIS dit DUPLESSIS conserved the use of DUPLESSIS as a “dit” name. Baptism and marriage records in the 1700’s reflect a mixture of SIROIS or DUPLESSIS appearing alone or together. It is likely though if you were introduced to one of Francois’ sons or their sons during this period they would give you DUPLESSIS as their surname. SIROIS was more likely to be used in formal interactions (i.e legal or religious). Québec conducted a census in 1762 following the burning of the South shore of the St Lawrence by the British in 1759. The sons of Francois thru his second wife were listed in Kamouraska as:

Augustin Duplessis
Joseph Duplessis
Maurice Duplessis
Pierre Duplessis

Most of the descendants of Francois dropped the DUPLESSIS “dit” name by 1850. The table below indicates the surname of current paternal descendants of Francois through his thirty-four known grandsons. To date I have only found one line of descendants who dropped the SIROIS name and kept DUPLESSIS . This line is through Joseph DUPLESSIS, grandson of Francois through his son Joseph and Marie Louise Claire Levasseur.  All of Joseph's descendants whom I have records for had dropped the SIROIS! name by 1900. Descendants of the other grandsons use SIROIS or a translation or an Anglicization thereof. The table below lists by grandson of Francois what surnames are in use by his descendants to whom the family name has been passed.

  (descendants of Francois Sirois dit Duplessis)

Many spelling variations of DUPLESSIS and some variations of SIROIS were recorded until standardized forms prevailed by about 1920. As descendants settled in English areas more fundamental changes in the surnames arose due to “translations”. 

SIROIS NAME VARIATIONS:

 DUPLESSIS NAME VARIATIONS:(for descendants of Joseph Duplessis)

It appears that Francois SIROIS dit DUPLESSIS was the only male to carry the name SIROIS who established himself in North America during its early European settlement and passed the SIROIS name on to generations of descendants. 

It is my belief  that over 99% of SIROIS in North America are related as descendants of Francois SIROIS. 

There is one SIROIS family in North America who actually adopted the SIROIS name as a “DIT” name and then retained it alone as their surname. Descendants of  William (Wellie) Lalancette dit SIROIS and Elisabeth Montreuil who were married on 28 Jan 1877 in St Basile, Madawaska, N.B,  dropped the Lalancette surname and retained SIROIS. 

Also of note: a search of phone directories in France also indicates a very small number of SIROIS listings (including variations). SIROIS appears to be a very uncommon surname today aside from those who can claim Francois as an ancestor.

Unlike the SIROIS name, the DUPLESSIS surname with its many spelling variations has arrived in North America via many different paths and DUPLESSIS who lived here today can claim many different origins for the name. I have not done a lot of research on this subject but will put forward in rough outlines some of the different origins of which I am aware.

This website is focused on the first DUPLESSIS family listed below, those who are descendants of Francois SIROIS dit DUPLESSIS.  Because of the many different immigrations and the different origins of the immigrants,  DUPLESSIS living in various parts of North America today are much less likely to be closely related than SIROIS are.  That said: