The term 'Sacro Attachment' refers to the connection between the sacrum and the ilium, which is part of the pelvic girdle. The ilium is a five-letter word that is used to describe the uppermost and largest bone of the pelvis. This bone is connected to the sacrum, which is the triangular bone at the base of the spine. Together, these two bones form the sacro attachment, which is an important part of the human skeletal system.