The origins of the plus sign remain mysterious. It may be a cousin of the ampersand, formed again from some compressed form of the Latin word Et, or “and,” but definitive proof has yet to be uncovered. And though ‘+’ has been used in programming since time immemorial, its debut on the web has taken rather longer.
When Google belatedly launched their social network in June 2011, the plus symbol figured heavily: Google+ was, of course, named for the character itself; user names on the service are signaled by a ‘+’ just as the ‘@’ precedes Twitter handles; and where Facebook encourages their users to “like” status updates, Google+ instead lets them “+1”.
Though it may seem as though Google was casting around for some character—any character—that was not indelibly associated with a rival social network, the plus sign, along with the concept of the “+1,” does have a degree of internet credibility in its own right. A 2004 entry in the Urban Dictionary (which, in this author’s experience, is both surprisingly reliable and reliably profane) explains that replying to a forum post with a terse “+1” signifies agreement, lending weight to the original post without requiring any greater investment on the part of the respondent.