The story
Blend of hashtag + flag, coined during the 2010 FIFA World Cup by Twitter when national flags were added to the end of three-character national abbreviation hashtags (e.g., #rsa or #jpn)
Etymology from Wiktionary, CC BY-SA 4.0.
hashflag
Today it means: A non-Unicode pictogram, similar to an emoji, automatically appended to a trending and often branded hashtag in a tweet. Full definition →