Most misspellings are a result of the coin being designed from a fraudulent model. Sometimes the models submitted for use in coin design were created by inexperienced or dishonest people. For example, the 1804 Draped Bust dollar misspell the word "LIBERTY" as "LIERTY". The reverse also spelled "UNITED" as "NITID".
Other times a misspelling is intentionally added as an "easter egg" or "designer's mark" by the coin's designer. Examples of this include the State Quarters with misspelling of the state names, such as OKLAMA and KENUCKY.
The coins designer, William Cousins, was fired after the coins were released. Although the mint tried to recall all the mispelled coins, some made it into circulation. Today those misspellings are highly collectible and valued at thousands of dollars.