In the English language, black sheep is an idiom that describes a member of a group who is different from the rest, especially a family member who does not fit in. The term stems from sheep whose fleece is colored black rather than the more common white; these sheep stand out in the flock and their wool is worth less as it will not dye. The term has typically been given negative implications, implying waywardness. In psychology, the "black sheep effect" refers to the tendency of group members to judge likeable ingroup members more positively and deviant ingroup members more negatively than comparable outgroup members. Source: Wikipedia (en)