When Google unveiled its new social networking venture a month ago, the first hurdle for early adopters was understanding the name: Google+. The brain trust in Mountain View could have called it “Google Plus,” but instead they have staked their claim to the plus sign itself (which is, ironically enough, quite difficult to Google for).

In fact, the Googlers had already been making use of the plus sign since March, when they introduced the “+1 button,” their equivalent of the Facebook “like” button. Used as an indicator for an online recommendation, it is, as Google’s announcement puts it, “the digital shorthand for ‘this is pretty cool.’” (Originally, you could “+1” listings in your Google search results; now, Google+ users can also “+1” anything appearing in their news “stream.”)

From the start, Google has been serious about making +1 into a verb, despite it not looking terribly verb-y. Whereas Facebook appropriated a well-established verb with like, +1 presents special challenges for joining the social-media “verbs of approval” club, along with digg, tweet, and favorite.

Well before the Web era, plus one (fully spelled out) could refer to an extra person who accompanies an invited guest to an event. The latest edition of the Oxford English Dictionary has examples of this usage back to 1977. While Google’s +1 might hark back to this earlier style of socializing, the more obvious inspiration derives from online forums and blog comment sections, where +1 came to be used as a quick way to agree with another poster’s opinion.

Converting the commenter’s informal thumbs-up into a standardized visual metaphor clearly involved a fair amount of thought from the Google team - including thinking through how this new activity could compete with Facebook’s “like” as an English verb. Google went so far as to include a page on “+1 spelling conventions” in its official documentation.

When a tech company is trying to tell you how to spell, you know something intriguing is happening in the world of language. Google may be wedded to +1 rather than plus or plus one, but if they want it to stick, their millions of users will have to figure out what to do with a “word” that is actually a symbol and a numerical digit - making it devilishly hard to punctuate and inflect.