Mulligan
An informal "do-over" shot, replayed without penalty, common in casual rounds, not allowed under the actual rules.
The exact origin is disputed, no version can be confirmed before the 1930s, but the most commonly told story credits a Canadian golfer named David Mulligan at a club near Montreal in the 1920s, who re-teed after a poor drive and called it a "correction shot," which his playing partners started calling a Mulligan instead. Whichever story is true, it's still not permitted under the actual Rules of Golf, only a casual, group-agreed exception.