The term "black sheep" refers to a person who is considered to be different from the rest of their family, group, or community, often in a negative way. This person may stand out due to their unconventional behavior, choices, or beliefs, leading others to view them as an outcast or someone who does not fit in. The expression highlights a feeling of being marginalized or isolated because of being different.
The phrase "black sheep" is thought to have originated from the wool industry; black sheep were considered less desirable because their dark wool could not be dyed, making them less valuable than white sheep. This concept of being less desirable led to the figurative meaning of someone who does not fit in or is seen as different in a negative sense.