eighteen (n.) Look up eighteen at Dictionary.com
late 14c., eightene, earlier ahtene (c. 1200), from Old English eahtatiene, eahtatyne; see eight + -teen. Cognate with Old Frisian schtatine, Old Saxon ahtotian, Dutch achttien, Old High German ahtozehan, German achtzehn, Old Norse attjan, Swedish adertån.