HODL is derived from the word "hold". It is a term used in cryptocurrency communities which means to hold instead of selling. For example, if the value of token is low then i will hold and wait for the right time. Selling is not always the key to make a good profit, but holding is. Oppurtunity is always around. You just need to wait and be patient. Others said that HODL is a british expression which means "hold on for dear life". Whatever meaning they give, when you are in the market just hold before you sell so you won't regret anything. Good luck and God bless!