Literal translation
Do good to Bertrand, he will pay it back to you by shitting on it.
Meaning
do good to Bertrand, he repays it with harm; ingratitude rewards kindness
Explanation
This proverb denounces ingratitude through a deliberately crude image: doing someone a good turn can be repaid with crude contempt in place of gratitude. Bertrand acts as a generic placeholder name, much like Pierre or Paul in French sayings: he embodies the ordinary recipient of kindness that backfires. The verb used, derived from the crudest word for defecating, gives the proverb its bite: the vulgarity of the gesture underscores how completely the good deed is overturned into insult. The construction places the harm as the direct, almost mechanical consequence of the good deed, as though describing a cruel and absurd law of human relations. It belongs to the coarsest register of speech and is used only in very relaxed conversation, never in front of children or in formal settings, to comment bitterly or with dark humour on betrayal following a favour. The original source already softened the final word with an ellipsis, a sign that even those who repeated the saying felt its crudeness.