A Korean slang / meme for 'Hello'. 'Bo-' is a prefix for Bokyem, a Korean famous
youtuber, and '-iru' means Hairu which is an old-fashioned
expression to say hi in South Korea. It was at first just how Bokyem say hi on his youtube channel, but spread through
the Internet as Bokyem became famous, and even people who are not a Bokyem's fan started to use this word.