What is tainted love?

"Tainted Love" is a 1964 song written by Ed Cobb, who composed the song while incarcerated in prison, inspired by both his religious faith and his experience of being imprisoned. Gloria Jones recorded it first and it was released in 1964. The better known version was released by British synth-pop duo Soft Cell, who recorded the song in 1981 and released it the following year. In the Soft Cell version, the expression refers to a sexual relationship between a prostitute and a priest, who confesses his sins to her without knowing her profession.