George Monbiot created this word in an article entitled Lest we forget in the Guardian on 11 November 2008: “There are plenty of words to describe the horrors of the 1939–45 war. But there were none, as far as I could discover, that captured the character of the first world war. So I constructed one from the Greek word ephebos, a young man of fighting age. Ephebicide is the wanton mass slaughter of the young by the old.”
The root appears in a few English words, including ephebe, the Greek word filtered through Latin that means a young man aged between 18 and 20 who undertook military service. Ephebiatrics is a rare medical term for the branch of medicine that deals with the study of adolescence and the diseases of young adults; an ephebophile is a adult who is sexually attracted to adolescents.
Though George Monbiot created it afresh, there is one previous example of ephebicide on record, in a work of 1979, Saul’s Fall: A Critical Fiction. This purported to be a collection of critical essays about a play by a forgotten Spanish author, but the whole book, including the play, was an invention by Herbert Lindenberger, now Emeritus Professor of Humanities at Stanford University.