A bromide is a phrase or platitude that, having been employed excessively, suggests insincerity or a lack of originality in the speaker employing it. [1]
The term "bromide" derives from the antiquated use of certain bromide salts in medicine as mild tranquilizers and sedatives. Administration of a "bromide" (such as the original Bromo-Seltzer prior to 1975 in the U.S.) would relieve anxiety and make the patient drowsy. Describing a phrase as a "bromide" is meant to humorously imply that it is a boring statement with similar soporific properties.