The story
Learned borrowing from the Latin phrase vestrā culpā (“through your (plural) fault”), ablative case of vestra culpa (“your fault, guilt”), used in English by analogy with mea culpa and nostra culpa.
Etymology from Wiktionary, CC BY-SA 4.0.
vestra culpa
Today it means: Your fault, due to your error; you are to blame. Full definition →