Note to Macbeth, 1.1.8: familiar

Act 1, Scene 1, line 8.
"In European folklore and folk-belief of the Medieval and Early Modern periods, familiar spirits (sometimes referred to simply as "familiars" or "animal guides") were believed to be supernatural entities that would assist witches and cunning folk in their practice of magic." —Wikipedia: Familiar spirit

Witch Feeding Her Familiars,
A Cat and Two Toads

Image Source: Wikipedia: Familiar spirit