Por Una Cabeza

Por una Cabeza is a tango song written in 1935 with music by Carlos Gardel and lyrics by Alfredo Le Pera.

The name is a Spanish horse-racing phrase meaning "by a head", which refers to a horse winning a race narrowly – by just the length of its head. The lyrics speak of a compulsive horse-track gambler who compares his addiction for horses with his attraction to women.

source: Wikipedia