Andy Aitkenhead was born in Scotland in 1904 and he was a mighty fine goaltender. These two factors helped create one of the great nicknames in hockey history; "The Glasgow Gobbler".
Aitkenhead played in every game for the New York Rangers in 1932/33 and 1933/34 and backstopped the Blueshirts to the Stanley Cup in '33. He finished fourth and fifth in the NHL in goals against average in the two years and was third with 7 shutouts in his second season. He would lose his job to Davey Kerr in 34/35 and finish his NHL career with 47 wins and 11 shutouts in 106 games while sporting a 2.35 GAA. His playoff stats were even better with a 1.48 average and 3 shutouts in 10 games.
Prior to his impressive NHL stint "The Glasgow Gobbler" had taken teams to both the Memorial Cup and Allan Cup finals by the age of 21. He turned pro with the Saskatoon Shieks of the Prairie Hockey League in 1926/27. In his second year with the Shieks he posted an average of 1.42 while the rest of the league had a 2.89 GAA. He was literally twice as good as any other goalie in the league. That's tough to do.
Upon transferring to the Portland Buckaroos in 1929/30 he posted 16 shutouts in 36 games and put up an average of 0.94. The rest of the North West Hockey League played to a GAA of 2.19, again he was more than twice as good as anyone else. To answer a question, yes, this is extremely rare in any league to have a GAA less than half of the rest of the league. Even some of the great goaltending years in history could not achieve this. When George Hainsworth had 22 shutouts in 1928/29 and an average of 0.92 the rest of the NHL had GAA of 1.50. Boston's Frank Brimsek came close in 38/39 when his average of 1.56 was near half of the rest of the circuit's 2.70.
So far, the only NHL goalie season I have found like Aitkenhead's was Bill Durnan in 1943/44. He had a GAA of 2.18 while the remainder of the NHL was at 4.46. Even latter day greats could only come close to being twice as good as the rest of their peers. Below are players with their GAA compared to the rest of the league.
Tony Esposito 1971/72 1.77 GAA/ Rest of League 3.13
Ken Dryden 1975/76 2.03 GAA/ Rest of League 3.49
Pete Peeters 1982/83 2.36 GAA/ Rest of League 3.91
Dominik Hasek 1993/94 1.95 GAA/ Rest of League 3.26
It's clear, that this is a rare feat in hockey, and even though it wasn't the NHL, "The Glasgow Gobbler" did it twice. He continued his terrific play through the 1930's, returning to Portland after his NHL stint. In 35/36 his average of 1.62 was again near halving the rest of the Pacific Coast League average of 2.85.
Throughout his fifteen year professional career, Aitkenhead would compile a record of 258-191-95 with a goals against average of 1.98 and 93 shutouts. He truly is one of the little known greats of hockey history.