Yetzweirtius was born in Bergues-Saint-Winoc in 1541, to a noble family of slender means. After travelling widely, he took service in the Army of Flanders as an ensign.Alphonse Roersch, "Jacobus Yetzweirtius", Biographie Nationale de Belgique, vol. 29 (Brussels, 1956), 873-876. He took part in the retaking of Oudenaarde in October 1572, writing a Latin verse account of the action that was published in Ghent. Little is known of his later life.
