Hypercorrection. Hypercorrection occurs when there is a discrepancy between the "correct" forms of a language and the way that language is actually spoken or written. When someone is worried about making a mistake, they will "correct" that possible mistake, even when no mistake has been made: this is called "hypercorrection" (meaning "too much correction").
Silent h. One of the most common forms of hypercorrection in medieval Latin has to do with the use of the letter "h" which was no longer pronounced. Since the "h" at the beginning of a word was often no longer pronounced, scribes would sometimes add an "h" at the beginning of a word, even when it was not necessary.