Hodl is a misspelling of “Hold” and an acronym for “Hold on for Dear Life”. It refers to keeping ownership of coins rather than selling them. This is a very popular word in the crypto community, especially in the bear market.
Someone wrote the word “hold” incorrectly on an early bitcoin forum, and users interpreted it as an acronym meaning “hold on for dear life”. It’s now something of a meme when prices are extremely erratic.