Why is home electricity supply called "mains"?

The word "mains" seems to be a widely understood synonym for home electricity supply.

Why is it called so? I always thought it was a corruption of main [electricity supply]. Is it an American dialect term? I mainly came across it in American jargon context, but Wiktionary says that it's a British term. What gives?

As Peter Shor mentioned, your Wiktionary link only makes a claim about the Norman word mains coming from minus.

Merriam-Webster gives for mains:

British
: of or relating to utility distribution mains mains voltage mains water

And etymonline gives for main:

Old English mægen (n.) "power, bodily strength, force, efficacy," from Proto-Germanic *maginam "power," suffixed form of PIE root *magh- "to be able, have power." Original sense preserved in phrase with might and main. Meaning "principal channel in a utility system" is first recorded 1727 in main drain.