Given names often turned into family names when people were identified by their father's name. For example, the first name Ahrend developed into the family name Ahrends by adding a genitive s-ending, as in Ahrend's son. Examples: Ahrends, Burkhard, Wulff, Friedrich, Benz.
So accordingly. 1  some crouching positions are squats. 2  some crouching positions may not be squats. 3  squatting is not implicity crouching.  squatting and crouching are terms with different but overlapping definitions, the former more specific to posture, the latter to 1  motivation. squat is not a synonym for crouch.
A person in the Trendelenberg position is lying supine with their head slightly lower than their feet. Abduction is movement away from the midline, or to abduct. Adduction is movement toward the midline, or to add. Flexion is to bend at a joint, or to reduce the angle.