Placebo is a Latin word meaning "I shall please". Placebo Domino in regione vivorum ("I shall please the Lord in the land of the living") is the first response in the Roman Catholic service of vespers for the dead - the service came to be known as "placebo" because of this.
A placebo is an operation, a chemical solution or a pill, which doctors administer as if it were a therapy, but which they suppose to have no therapeutic value. Physicians typically use placebos only in the context of a clinical trial, in which a "test" group of patients receive the therapy being tested, and a "control" group receives the placebo. See Placebo effect.
Placebo is also a Swedish/British/American band that formed in London in 1995.
