Where does the term flashing come from? The term flashing in Android communities seems to be interchangeable with "Install"


  Because Google's apps are not open source, custom ROMs can't bundle Google's apps -- like Gmail, Hangouts, or the Play Store -- with their ROMs. That means you'll need to download and flash them separately.


From How To Flash A ROM To Your Android Phone

So if this is the case where does the term flashing come from?
ROM is a short for read-only memory. Nowadays, it is often a writable memory that is not written in normal operation. In past days, it used to be rather EPROM/EEPROM.

The term flashing probably comes from era of EPROM, which can be erased using a strong UV light. Erasure of whole memory is needed before EPROM is written. This is not the case of current flash memories, but the term “flashing” remains.