Meaning: The accomplishment of three successes or wins.
NOUN: Sports 1. Three goals scored by one player in one game, as in ice hockey. 2. Three wickets taken in cricket by a bowler in three consecutive balls. 3. Three consecutive wins or outstanding accomplishments by the same individual, such as a jockey in horse racing.
ETYMOLOGY: From the hat with which the feat was traditionally rewarded in cricket.
Alternatively,
It comes from the days when it was common for men (and women for that manner) to wear hats to social events, and in Canada a hockey game is a social event. If a player scored three goals in one game, appreciative fans would throw their hats onto the ice.