US President Donald Trump has recently described the murder of a journalist in Saudi embassy in Turkey as being committed by "rogue killers". I first came across rogue in the context of rogue planets, which seem to be orbiting no mother star. I've looked up the word rogue in multiple dictionaries and yet I couldn't confirm what he meant by rogue killers, that's when I thought, "maybe a bit of etymology could help decode the word." One etymology theory links the noun rogue with roger “a beggar pretending to be a poor student”, but that doesn't explain why a a rogue elephant or planet came to mean living apart, separate, unusual and/or dangerous. Does rogue killer mean a dishonest killer, an uncontrolled killer (perhaps rogue killer robots?) or something else?
Learn English – What does “rogue killers” mean
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Best Answer
The astronomical use of "rogue" is somewhat based on the original dictionary meaning:
When something is described as "rogue", it normally implies it acts under its own volition, without constraint from some governing body or authority. A "rogue killer" is someone who works alone and who kills in an unpredictable way or for obscure reasons. Trump calls Khashoggi's killers "rogue" to suggest they were not acting under any official orders (presumably from the Saudi royal family).
A "rogue planet" is one that is similarly unattached to any sun or solar system, although obviously without any sinister or dangerous agenda.