Depending on your source, organized hockey began to matter at a variety of different times. Most often 1917 is used as the cutoff date, when the National Hockey League was born. Of course, the line between the NHL and its immediate predecessor, the National Hockey Association, is a purely political one. So anyone using 1917 as their starting point really needs to be using 1909 instead, but that's beside the point.
If you go back further than that, generally you'll be looking at 1893 as the starting point, which was the first year that the Stanley Cup was awarded. Surely the Stanley Cup is what matters after all, right? Not really. The Cup was first awarded to that season's champion of the Amateur Hockey Association of Canada (AHAC), an existing hockey league. The structure of that league didn't change just because a new trophy was introduced.
So a very few histories of the game stretch back to 1887, the first year of the AHAC, but these seasons are not treated with nearly the same respect as the Stanley Cup era, for whatever reason. Modern eyes see the Stanley Cup as the ultimate prize in hockey, and so look back on the history of the game with that in mind. But organized hockey predates the Stanley Cup by many years, and these years are not to be ignored.
Before even the AHAC, there was the Montreal Winter Carnival hockey tournament, which was first played in 1883. This is now considered the first Canadian hockey championship, and was also played in 1884 and 1885 before the formation of the AHAC. No carnival tourney was played in 1886, but several Montreal teams instead played a tournament amongst themselves that season. Surely these years are worthy of our attention as well.
We're now as far back as anyone has really gone - full details of the 1883 Winter Carnival results aren't even available. But hockey clubs did not suddenly spring up to play in this tourney. McGill University's hockey club was formed in 1875, and the Quebec City club in 1878. The Montreal Victorias club originated in 1874, 1877 or 1881, depending on your source. I suggest there is approximately a 0% chance that these clubs never played against each other until the 1883 carnival, but we just don't have any details of these matches yet. This is one area of hockey history that needs far more attention.
Early organized hockey in other parts of the country need more work as well. The Rideau Rebels are a well-known name, being formed in 1884, but we don't know much about the games they actually played. Queen's University and the Royal Military College in Kingston, Ontario first played against each other in 1886. The Queen's club played its first game in 1884. Not much is known about these teams. A team from Dartmouth, Nova Scotia travelled to Quebec to challenge AHAC teams in 1889 (the AHAC technically covered the Atlantic provinces as well). Surely this team also did not spring out of nowhere. But we know little about Nova Scotia hockey at that time.
Hockey did not start to matter in 1893. We need to go back further than that, and to do so will require a lot of research. I've been working on some of it in the past year, but there's much more to do.