Mulligan is golfing jargon for an extra stroke after an especially poor swing that is not counted on the scorecard. The origin is unknown, although it seems likely that there was once a really poor golfer named Mulligan whose partners would allow him extra strokes. But if this is true, his identity is now lost to the ages.
The term dates to at least 1938 when it appears in the Coshocton Tribune (Ohio) of 16 April:
A “mulligan” is a golfing handicap which allows a golfer to re-play any one tee shot he chooses to.
(Source: Oxford English Dictionary, 3rd Edition)
Copyright 1997-2013, by David Wilton