It probably existed way before Smartphones (in another context) but I'm curious on who used it on Mobile Devices for the first time. Was it Apple? Was it someone else?
I saw this tweet yesterday.
Although Xerox seems to be the first to use it on computer, there is no definite data (yet) on who used it on the phone first.
The icon is to be seen on the iPhone 3 back in June 2007 in some of their standard apps. That, to me, seems to be the first appearance on mobile phones, because other companies or apps that are named in the "first hamburger discussion" came later.
Like Google. Google is being named somewhere else on the interweb as potentially being the one who introduced the icon to mobile phones with Chrome. But Chrome's first beta was released in 2008 and the first Nexus phone was released in 2010.