The Prince of Cumberland is a title Duncan gives to his son Malcolm. It, like the Prince of Wales, signifies that the person who gets it is the heir apparent to the throne. By giving the title to Malcolm, Duncan makes it less likely that Macbeth will inherit the throne from him.
Macbeth views this as a stumbling-block which will prevent the witches' prophecy from coming true.
Malcolm, King Duncan's son, is proclaimed Prince of Cumberland in Act I Scene 4
After Macbeth, Banquo, and King Duncan exchange warm greetings, King Duncan announce Malcom as the Prince of Cumberland.
In Macbeth? King Duncan names his son Malcolm The Prince of Cumberland who is the heir apparent. After his murder, Malcolm flees so Macbeth is named to be King but later on in the play Malcolm, Duncan's son, becomes king.
As in England calling your son the Prince of Wales marks him as the heir apparent, Duncan's calling Malcolm the Prince of Cumberland marked him as the next king. This would certainly be "a step on which [Macbeth] must fall down, or else o'erleap."
Duncan's older son Malcolm. He is named Prince of Cumberland in Act I, Scene 5, Lines 44-45.
The suggestion is that the title was like the Prince of Wales: it was the title of the heir apparent.
Duncan rewards Macbeth by making him the Thane of Cawdor. Not exactly the reward Macbeth was looking for, though--he wanted to be made the Prince of Cumberland.
Macbeth says this quote in William Shakespeare's play "Macbeth." He is referring to Malcolm, the Prince of Cumberland, as an obstacle standing in his way to the throne. Macbeth contemplates whether he should let destiny take its course or take action to achieve his ambition.
A Prince of Cumberland would be a prince who is the son of a prince who is Duke of Cumberland. For example, Prince George of Cumberland when his father, The Prince Ernest Augustus, was The Duke of Cumberland.
Duncan names his son, Malcolm, as the Prince of Cumberland. This is significant because it indicates that Duncan plans for Malcolm to succeed him as king of Scotland, bypassing Macbeth in the line of succession. It highlights the political and power dynamics at play in the play "Macbeth."
Malcolm being named Prince of Cumberland makes him the heir apparent to the Scottish throne, putting him in a strong position to challenge Macbeth for the crown. It also highlights the legitimate claim Malcolm has to the throne, further emphasizing Macbeth's position as a usurper.
Malcolm, King Duncan's son, is proclaimed Prince of Cumberland in Act I Scene 4
After Macbeth, Banquo, and King Duncan exchange warm greetings, King Duncan announce Malcom as the Prince of Cumberland.
In Macbeth? King Duncan names his son Malcolm The Prince of Cumberland who is the heir apparent. After his murder, Malcolm flees so Macbeth is named to be King but later on in the play Malcolm, Duncan's son, becomes king.
In Act 1, Scene 4 of Macbeth, the next in line of the throne after King Duncan would be his son, Malcolm. He is the Prince of Cumberland and the Prince of Scotland, making him the heir apparent to the throne.
As in England calling your son the Prince of Wales marks him as the heir apparent, Duncan's calling Malcolm the Prince of Cumberland marked him as the next king. This would certainly be "a step on which [Macbeth] must fall down, or else o'erleap."
The act of King Duncan naming Macbeth as the Prince of Cumberland clears the way for Macbeth to become king in Scotland, as it puts him in line for the throne. This act is seen as a threat by Macbeth, prompting his ambition to seize the crown.