While it has been in use for a long time, the expression was popularised from the twentieth century by heavyweight boxing champion Muhammad Ali, who, in 1964, declared himself "the best" soon after defeating Sonny Liston. The phrase 'greatest of all time' is bandied a few ton in sport nowadays. https://keegangdrgc.ambien-blog.com/46617528/rumored-buzz-on-what-is-goat-in-football