This family is a rare case of the "dit" nickname becoming the actual surname. Modern descendants spell it Lagacé, or Lagace, or sometime Lagasse.

The earliest known ancestors are Michel Mignier and his wife Catherine Masson, who were farmers on the tiny Île de Ré, at the mouth of the Garonne near La Rochelle. Michel was born in nearby Aunis c1602, and died on the Île de Ré in May 1678. He married Catherine in May 1635. She died there as well, and was buried on March 10, 1669.

Their son André was born in 1640, and in 1665, as a member of the Carignan Regiment (the regiment "Compagnie de l'Allier"; these marines were ancestors of many French-Canadians) he was sent to Québec City to protect settlers against Iroquois raids. At that time the regiment (a private one, organized by the Prince de Carignan) had just returned from fighting the Turks in Hungary. André was evidently known by a nickname, "la gachette," which literally means "trigger," but in this case "good marksman." This was the source of Lagacé. In October 1668, having decided to stay in Canada when the regiment returned home, he was granted land at Charlesbourg, and one week later married Jacquette Michel or Michaud (widow of Jean Cardin) in Québec City. In 1672 they bought an additional 15 acres for the price of one chicken and a small annual money payment. In 1685 he moved his family to Rivière-Ouelle, and died there in November 1727. Jacquette died November 28, 1710 at Rivière-Ouelle.

Their children: André (1669-1729, married Marie-Charlotte Pelletier and Françoise Ouellet, lived at St-Anne de la Pocatière); Marie (1671-1681); Françoise (1674, married Robert Morin); Marie-Anne (1677, married Philippe Boucher); Marie-Madeleine (1679, married Nicholas-Claude Lizot and Félix Aubert); and Michel (1682, married Angélique Thibault, 10 children, and Marie-Louise Pinel, no children).

Michel Mignier dit Lagacé was born April 18, 1682 in St. Joseph, Québec; he died sometime after 1739. He was evidently the youngest of the six children. His first wife was Marie-Angélique Thibault, born February 15, 1685/86 in Cap-St-Ignace, Québec. They were married July 28, 1705 in St-Ignace, Cap St-Ignace, Québec. Their children: Marie-Madeleine (1706, married Joseph Soucy and Antoine Michaud); Michel (1708-1709); Marie-Angélique (1710, married Jacques Bois); Geneviève (1712, marreid Charles Pelletier); another Michel (1714, married Marguérite Pelletier); Joseph (1716, married Geneviève Caron and Marie-Anne Ouellet); Marie-Françoise (born and died 1719); Jean-Bernard (1720, married Marie-Brigitte Pelletier and Marie Dumont); Marie-Josèphe (see below); and Marie-Anne (1724, married Louis Grondin).

Marie-Josèphe or Josette Mignier dit Lagacé was born October 2, 1722 in La Pocatière, Québec and married Pierre Jean on February 6, 1741/42 in Ste.-Anne-de-la-Pocatière. They were the patrilineal great-great-grandparents of Marie Eva Jean Martin.

There is a Mignier dit Lagacé family association, from whose website I got much of this information.