I am almost sure it stands for External such as "External causes of injury and poisoning".

ICD-9 E and V Codes: E-external causes of injury V-supplemental classification

Chapter 16 is the chapter in the ICD-10 that contains codes for the perinatal period.

The ICD-10 is the 10th revision of the International Classification of Diseases, which is a medical classification list by the World Health Organization (WHO). It is used for coding diseases, signs, symptoms, abnormal findings, complaints, social circumstances, and external causes of injury or diseases. The ICD-10 is widely used for epidemiological research, clinical purposes, and billing and insurance reimbursement.

The icd-9 code for Brain Injury (non specified) is 854.00. icd-9 codes from 800 - 999 all relate to brain injury with more description of symptoms/causes