People were confused by “the standby state.” It seemed counter-intuitive for an electronic device to be neither on nor off. So, after the IEEE nicked the ICE’s standby button (remember?), it decided some rechristening was in order. 


The governing body re-named standby mode “sleep,” to invoke the state where humans are neither on nor off. 


Today, a crescent moon is the de facto sleep state symbol on devices in the US and Europe. Its metaphorical power is undeniable! Travel to Japan, though, and you’ll probably see the occasional Zzzz button.


via The Secret Histories of Those @#$%ing Computer Symbols