In the first scenes of "Macbeth," the name Sinel is mentioned. Who is Sinel?
The line you are referring to is in Act I, scene 3:
Stay, you imperfect speakers, tell me more.
By Sinel's death I know I am Thane of Glamis;
But how of Cawdor? The Thane of Cawdor lives,
Macbeth is talking to the witches, who have just welcomed him by calling him Thane of Glamis, Thane of Cawdor, and King hereafter. Macbeth knows that he is Thane of Glamis because of "Sinel's death," but they set him to wondering how he could possibly get the other titles.
"Sinel" is the name Shakespeare gives to Macbeth's father. Since the father is dead, the title has passed down to his son. The historical Macbeth's father was named Findlaech.
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