In Macbeth who are Graymalkin andPaddok?

In William Shakespeare's play "Macbeth," Graymalkin and Paddok are familiars, or spirits, associated with the witches. They are mentioned in Act 1, Scene 1, when the witches gather to plot their mischief:

"Thrice the brinded cat hath mew'd.

Thrice and once the hedge-pig whined.

Harpier cries: 'Tis time, 'tis time."

It is believed that "brinded cat" refers to Graymalkin and "hedge-pig" to Paddok.