Short for therapist wear.
Have you ever seen a therapist? They're likely wearing a particular flavor professional clothing, therwear.
Therwear commonly includes tweed jackets, scarves, pantsuits, flowy blouses, v-neck sweatshirts with ties. The bay area is known for an aging hippie flavor of therwear, particularly female therapists. Male therapists often wear jeans and a tucked in button up shirt to appear "hip."
Dr. Newton has some bitchin' therwear. Did you his sweet ugly tie, it goes really well with his beard.