If you look in a dictionary, the general meaning of HODL means holding on for dear life. In the cryptocurrency industry, it means holding your crypto coins instead of selling them. By holding your crypto coins, you're not day trading for profit, or selling to minimise losses, but holding until you're in a position to make a significant positive gain.
The term originated from a bitcoin forum postby a guy called "GameKyuubi" on December 18th 2013. He intended to title the post "I AM HOLDING", but for some reason, after typing it twice, it read "I AM HODLING". He acknowledged the spelling, and continued his rant.
He went on about being a bad trader and acknowledging that he's a bad trader. An epic rant it was whereby he states that he cannot accurately predict the ideal buying points and selling points in the market. Seriously, how many people can accurately predict these swings continuously? The market is the market is the market. It can change so suddenly without warning!
He goes on to advise everyone in between to hold their coins. The post naturally blew up and everyone started holding their coins. And a new group of people was born called Hodlers.
Aside from hodling to make profit or mitigate losses, a true hodler believes in the crypto currency of the project that he/ she is investing with and will not be bothered by "crashes or spikes" in the market. I myself tried trading with my first investment in crypto and was awful at it, even though I was following the signs and analysis techniques. I am a HODLER. Through thick and thin.