pillar (n.) Look up pillar at Dictionary.com
c.1200, from Old French piler "pillar, column, pier" (12c., Modern French pilier) and directly from Medieval Latin pilare, from Latin pila "pillar, stone barrier." Figurative sense of "prop or support of an institution or community" is first recorded early 14c. Phrase pillar to post is c.1600, originally of tennis, exact meaning obscure.