b. Prefixed to titles of rank after late L. usage in excōnsul, nom. evolved from ex cōnsule ‘from (being) consul’, (hence) lately consul; whence gen. with the sense ‘former’, as in ex-professor, and by further extension prefixed to adjs. (after ex-consular XVII) or to sbs. used attrib., as ex-service.
c. In commercial use, with ref. to goods, ‘out of’, ‘landed from’ (a ship); similarly ex-warehouse; ‘without’, ‘exclusive of’, as in ex-dividend.
"ex." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. (November 20, 2018). https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/ex-4
"ex." The Concise Oxford Dictionary of English Etymology. . Retrieved November 20, 2018 from Encyclopedia.com: https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/ex-4