Mea culpa
Mea culpa ( Latin "through my fault") are words from the Confiteor , which has been spoken in the Catholic Church since the 11th century :
" Confiteor [...] quia peccavi nimis cogitatione, verbo, opere et omissione:
mea culpa, mea culpa, mea maxima culpa [...] "
"I confess [...] I have sinned in thoughts, words and works:
through my guilt, through my guilt, through my great guilt [...]"
The believers beat each other on the chest.
The expression mea culpa has entered colloquial language, often ironically, as an excuse. Occasionally the term is used generically to refer to a far-reaching or meaningful request for forgiveness.
Web links
Wiktionary: mea culpa - explanations of meanings, word origins, synonyms, translations