It's most often referred to in the electricity sector, where bringing power up after a major regional blackout (think 2003 NE blackout) is extremely nontrivial, since the normal steps to turn on a power plant usually requires power: for example, operating valves in a hydro plant or blowers in a coal/gas/oil plant, synchronizing your generation with grid frequency, having something to consume the power; even operating the relays and circuit breakers to connect to the grid may require grid power.

The idea here is presumably that Google services have so many mutual dependencies that if everything were to go down, restarting would be nontrivial because every service would be blocked on starting up due to some other service not being available.