In 1920s America, the # sign served as a shorthand for weight in pounds (and they still call it the pound sign). It was first brought to a wider public thanks to its adoption by telephone engineers at Bell Labs in the 1960s as the generic function symbol on their new touch-tone phones – and if you're looking to sound clever, you could call it an "octothorpe", the tongue-in-cheek term coined at Bell to describe it. It's on Twitter, though, that hashtags have really come into their own, serving as a kind of function code for social interaction #ifyoulikethatkindofthing.
There's a special place in my heart for the supremely useful three letters of "meh", which express an almost infinitely flexible contemporary species of indifference. In its basic exclamatory form, it suggests something along the lines of "OK, whatever". As an adjective, it takes on a more ineffable flavour: "it was all very meh". You can even use it as a noun: "I stand by my meh." Apparently first recorded in a 1995 episode of The Simpsons, some theories trace meh back to the disdainful Yiddish term mnyeh. Its ascent towards canonical status, though, embodies a thoroughly digital breed of boredom.
Also known as "auto-correct errors", a Cupertino error occurs when your computer thinks it knows what you're trying to say better than you do. The name comes from an early spell checker program, which knew the word Cupertino - the Californian city where Apple has its headquarters - but not the word "cooperation". All the cooperations in a document might thus be automatically "corrected" into Cupertinos. Courtesy of smartphones, Cupertinos today are a richer field than ever – a personal favourite being my last phone's determination to transform "Facebook" into "ravenous".
Tom has a few more examples over at The Guardian: Link