Addison:
1) An enormously popular name for girls.
2) The name of a debilitating disease, from which the late President John F. Kennedy is documented to have suffered.
(Addison's Disease is very rare in occurrence, but it is not obscure. Even brief biographies of JFK explain that he suffered from an extremely painful condition named Addison's Disease. Therefore, the "disease association" is unlikely to ever be unfamiliar to Americans.)
Alexia:
1) A name pushed by many baby name book authors as a version of Alexandra (or Alexis).
2) A medical condition related to dyslexia, which causes a person to suddenly lose the ability to read
Parents who read "The Baby Name Workbook" will not fall victim to selecting names with significant, alternate definitions.