A misspelling of ‘hold’ that stuck around to mean ‘keep’.
A cryptocurrency trader who buys a coin and does not see himself selling in the foreseeable future is called a HODLer of the coin.
If a person says in a conversation “I am hodling.” or says to you, “You should hodl!”, this person believes the coin will be profitable in the future.
The very first time the term HODL appeared on the Bitcoin talk forum was in 2013 and came from a member named GameKyuubi under the thread “I AM HODLING”.
“HODL” was originally a typo which has now popularly earned the status of a humorous backronym: “Hold on for dear life!”