So doesn't it seem likely that 'turn on' the light comes from gas lamps which predated electric ones, and is about turning on the supply of gas (rather than the supply of beer as Capfka first suggested)?

Admitted and acknowledged non-sequitur:
On the radio recently I heard an interview with some war artists about their experiences. One of them talked about arriving at a military base in Iraq and described all the noise and activity, with 'soldiers coming and going, helicopters taking on and off' etc etc etc.
I could follow how this had happened in speech and I knew what he meant (at least I assume I do!), but my mind blanked at visualising a helicopter 'taking on'. Taking on what? Or just taking on as in having a hissy fit or tantrum? I rather liked it!