Mea Culpa Means My Fault in English

Mea culpa is a Latin phrase that translates into English as "my fault", or "my own fault". In order to emphasize the message, the adjective "maxima" may be inserted, resulting in "mea maxima culpa," which would translate as "my most [grievous] fault."

Origin
The origin of the expression is from a traditional prayer in the Mass of the Roman Catholic Church known as Confiteor (Latin for "I confess"), in which the individual recognizes his or her flaws before God. The "mea culpa," as the Confiteor has come to be known popularly, is not simply a confession of sins, but rather an admission of one's flawed nature and the willingness to make amends for it.

Popular meaning
In the popular vernacular, the expression "mea culpa" has acquired a more direct meaning, in which, by doing or performing a "mea culpa", someone admits to having made a mistake by one's own fault (meaning that it could have been avoided if that person had been more diligent). It may be used even in trivial situations: if a football player, for instance, admits that his team lost a game because he missed a field goal, this may be called a "mea culpa", meaning that he admitted his mistake, which he could have avoided (at least in theory), and that resulted in a subsequent evil. In today's American vernacular, people often say "my bad."

In some countries, phonetical versions of the phrase are used with the same meaning. For instance, in Slovenian, the phrase "Moja Kolpa" is often used, sounding almost the same, but literally meaning "My Kolpa" (Kolpa is a river in Slovenia).

SOURCE: Wikipedia