Recently, Michael Quinion explained that the term “unfriend” is much older than Facebook.
In a recent edition of WORLD WIDE WORDS (Issue 667, Saturday, November 28, 2009) he suggests that the word originates in medieval Scotland:
The noun certainly is, with evidence going back to medieval Scots, its sense ranging from that of a person with whom one is not on friendly terms to a full-blown enemy. After going out of favour around 1600 it was reintroduced by Sir Walter Scott in 1814 but then disappeared again. The verb has been recorded but is very rare, though the adjective “unfriended” has been moderately successful for some centuries.
Though it doesn’t mean that there isn’t some contemporary animosity towards the term as some people perceive “unfriend” as clumsy:
It was chosen as Word of the Year 2009 by the New Oxford American Dictionary. Christine Lindberg, senior lexicographer for Oxford’s US dictionary programme, was quoted as saying “Unfriend has real lex-appeal.” She wrote in the Dictionary’s blog: “It has both currency and potential longevity. In the online social networking context, its meaning is understood, so its adoption as a modern verb form makes this an interesting choice for Word of the Year.”
The New Oxford American Dictionary’s editors have been criticised for selecting it (Frank Schell in the Chicago Tribune called it “an act of wanton barbarism”) and the word itself has gained few friends among writers (The Irish Times remarked that it would “cause lovers of the English language to wince”). The main objection to it — apart from its inelegance — is that it ought to be defriend, a verb that’s also used, which would parallel the standard befriend. However, the editors of the New Oxford American Dictionary found that unfriend was much more common. It is presumably modelled on terms such as unsubscribe. What makes it odd is that few verbs are created using the un- prefix and that the verb sense of friend is itself rare.