I recently published a book, “Body Language - from Head to Toe”, that combines my interest of American idioms, slang, and other expressions with my understanding, as a surgeon, of the importance of anatomy.
“Body language” usually refers to feelings, emotions, and intentions expressed by various forms of nonverbal communication, including positioning the body or parts of the body in different ways, gestures, eye movements, and facial expressions. For example, a smile indicates that one is happy or pleased, a frown that one is worried or angry, etc.
In contrast, body language in the book “Body Language - from Head to Toe” refers to the use of body parts (anatomy) in the spoken or written language. Such words occur in many idioms, slang, and other expressions, and the book is a collection of them.