UK here. It's definitely been in use as journalistic jargon for a while, typically in the form of a headline "Explainer: <topic of article>", e.g. http://www.th

UK here. It's definitely been in use as journalistic jargon for a while, typically in the form of a headline "Explainer: <topic of article>", e.g. http://www.theguardian.com/commentisfree/libertycentral/2009/feb/24/freedomofinformation-civil-liberties http://www.theguardian.com/commentisfree/libertycentral/2009... (2009); here's a trend graph that shows that usage has picked up in the last decade: http://www.google.com/trends/explore#q=explainer http://www.google.com/trends/explore#q=explainer Earliest citation I've been able to find (1998): http://books.google.co.uk/books?id=kw9lAAAAMAAJ&q=%22an+explainer+on%22&dq=%22an+explainer+on%22&hl=en&sa=X&ei=uOBPU7D4H6fT7AbHl4HgDw&redir_esc=y http://books.google.co.uk/books?id=kw9lAAAAMAAJ&q=%22an+expl... - note that this is US, not UK. Article on "explainer" journalism; a little informal but demonstrates usage: http://www.theawl.com/2014/03/eleven-questions-about-explainer-journalism http://www.theawl.com/2014/03/eleven-questions-about-explain...