Hypercorrection is a nonstandard use of language that comes from overapplying a perceived grammar or pronunciation rule. Speakers usually produce it while trying to sound more correct, formal, or educated.
A common English example is saying "between you and I" instead of "between you and me," after being taught that "you and me" is wrong in sentences like "You and me went." Using "whom" where "who" is grammatical is another frequent case.
Source: Hypercorrection, Wikipedia