In my personal experience, I first heard of it 1 year ago in a online forum game, people sold gold for Bitcoins, around March, gave it no importance at first. Now im kinda utterly commited to it. Really an interest subject of study.
Well, based on my own experience, I have first heard bitcoin in our school when my classmates are talking about a certain topic in which they include the statement that they can earn their own income through online in which they literally do not work on a physical basis. By this, I got curious so I joined their discussion about that and found out that it was bitcoin cryptocurrency so I asked them to explain it further more so I can easily understand it and now, I am already engaged into it.