The term originated from the occasional black sheep which are born into a flock of white sheep due to a genetic process of recessive traits. Black wool was considered commercially undesirable because it could not be dyed. In 18th and 19th century England, the black color of the sheep was seen as the mark of the devil.
The transom is the flat back end of a boat. Some boats are pointed on both ends, so they have no transom. A traditional canoe, pointed on both ends has no transom. A modern square stern canoe (made to take an outboard motor) has a transom.
Levo-Transposition of the great arteries is an acyanotic heart defect in which the primary arteries are transposed, with the aorta anterior and to the left of the pulmonary artery, and the morphological left and right ventricles are also transposed.ongenital heart diseases involving only the primary arteries (pulmonary artery and aorta) belong to a sub-group called transposition of the great arteries.