If you're reading this blog, chances are that you know what rovers, points and cover-points are. Or were. They're part of the history of the game; before defencemen we had points and cover-points (or simply covers), the former playing close to the goalkeeper, and the latter being a conduit between the defence and the forwards. The rover was phased out of eastern hockey around 1911/12, while the point/cover positions morphed into side-by-side defenders soon thereafter.
But that's not all there is to the story of positional changes in hockey. If you go far back enough, specifically to 1875 when the first organized, indoor games between two opposing clubs took place in Montreal, there were typically nine men on the ice for either side, rather than the seven we're used to dealing with in early hockey history. They played four forwards as we're used to from the rover era, but had two extra men on defence. Not only that, but the defensive positions were not yet called point and cover, they were back and half-back, a clear indication of the fact that the rules of the game were adapted from football.
I can't be 100% of how the players typically lined up, but I think the following makes sense. The goalkeeper is marked with GK, the backs with B, the half-backs with HB, and the forwards with F.
However, they did not immediately adopt the seven-with-a-rover lineup. They dropped a back and a forward, still playing with two half-backs, thusly:
here). That opened the ice up a bit, and brings us close to the setup we're used to today:
The usual caveats for this sort of general discussion apply, of course. The years mentioned may not be entirely precise, and it's unlikely that every team adopted the same lineup at the same time. Each change would have taken a bit of time to become standard.