When did "Twerking" and "Selfie" enter the dictionary?

I read in the news that twerking and selfie have been added to dictionary recently. Did it give any origin? Is there any information or details about them?


Solution 1:

They were both added to Oxford Dictionaries Online last month.

The origin of twerk is given as ‘1990s: probably an alteration of work’ and of selfie as ‘early 21st century: from self + -ie’.