Ah now I understand what you folks are saying - a Mae West is a life vest. NEVER heard that before in my life.

Mae West for cake: well, it was designed with her in mind. The yellow frosting (blond hair), white cake (for a look of purity) and chocolate covered (for the sinful side).

It is also used as a nickname for French people in Québec. On their work breaks French people will most often have "un Mae West pi un Pepsi" (a Mae West and a Pepsi). We were the biggest consumers of both these items in Canada for the longest time. So both these terms are used to describe French Québecers.