yes I agree we should define Yarn, but what we are building is not that special to the end users, who I images will just be confused about what twt, yarn, thooth etc. are. compare to using familiar words like post and tread. Tread also binds nicly with the yarn as a overall concept :)
For the technical layer, then yes, we should have a vocabulary that can be closer to the “metal”, but not in the UI