I always assumed we just called it hydro in BC because so much of the power comes from hydroelectric, but then I moved and it seems we call it hydro everywhere no master source..?
The name of the utility companies in most provinces was probably an influence. Until 1999 in Ontario it was the Ontario Hydro-Electric Power Commission, shortened normally to Ontario Hydro. Manitoba Hydro. Hydro Quebec. I think in Toronto they still stamp manhole covers with THES (Toronto Hydro-Electric System).
If I remember correctly, Hydro One also serves some parts of the Ottawa area, and their delivery rates were different enough from Hydro Ottawa that it was often a material consideration for where one chose to buy one's house.
https://www.aeso.ca/aeso/understanding-electricity-in-albert...