Bromide

Bro·mide

Bromide

n.
  1. A compound of bromine with a positive radical. (Chem.)
  2. A person who is conventional and commonplace in his habits of thought and conversation. [Slang]
    The bromide conforms to everything sanctioned by the majority, and may be depended upon to be trite, banal, and arbitrary.
    — Gelett Burgess.
  3. a conventional or trite saying; -- often used in the phrase “old bromide”.