c.1300, ancestre, antecessour, from O.Fr. ancestre (12c., Mod.Fr. ancêtre), from L.L. antecessor "predecessor," lit. "foregoer," agent noun from pp. stem of L. antecedere "to precede," from ante- "before" (see ante) + cedere "to go" (see cede). Current form from early 15c. Feminine form ancestress recorded from 1570s.

From Bouviers 1883:

One who has preceded another in a direct line of descent; an ascendant.

A former possessor; the person last siesed.
Terms de la Ley; 2 Bla. Com. 201.

In the common law, the word is understood as well of the immediate parents as of those that are higher; as may appear by the statute 25 Edw. III., De natis ultra mare, and by the statute 6 Ric. II. c. 6, and by many others But the civilians relations in the ascending line, up to the great-grandfather's parents, and those above them, they term majores, which common lawyers aptly expound antecessors or ancestors, for in the descendents of like degree they are called posteriores; Cary, Litt. 45. The term ancestor is applies to natural persons. The words predecessors and successors are used in respect to the persons composing a body corporate. See 2 Bla. Com. 209; Bacon, Abr.; Ayliffe, Pand. 58; Reeve, Descents.

also “Ascendant” also “Majores” means a Man who has preceded another in a direct line of descent