Members of the same group, profession, or social circle tend to protect one another rather than competing destructively. There is honor or self-interest in not attacking your own kind.
The observation that dogs of the same pack do not attack one another with lethal force was documented by Aristotle and became a widespread metaphor in European writing. In Italian the proverb took root in the context of guild culture and professional solidarity: craftsmen of the same trade, merchants of the same city, or members of the same family were expected to maintain a basic code of mutual protection even in competitive circumstances. The proverb is recorded in Italian collections from the sixteenth century and has a close Latin precursor. It carries a dual resonance: positive (solidarity among peers is a moral value) and negative (closed professional networks protect their members from accountability). Today it is frequently used in the latter, critical sense — to describe lawyers who do not sue each other, politicians who do not investigate their colleagues, or doctors who close ranks when malpractice is suspected. The phrase 'omertà professionale' (professional silence) is a related concept. The English 'There is honour among thieves' captures a similar idea about in-group protection, though applied to criminals rather than professions.
Rooted in Aristotelian natural observation; in Italy linked to guild and professional solidarity culture of the medieval and Renaissance periods.
Legal profession
Non troverai un avvocato disposto a fare causa al suo collega — cane non mangia cane.
You won't find a lawyer willing to sue his colleague — dog doesn't eat dog.
Political corruption
Nessuno dei deputati ha parlato dello scandalo. Cane non mangia cane.
None of the MPs spoke about the scandal. Dog doesn't eat dog.
Medical complaints
Il medico ha difeso il collega nonostante l'errore — cane non mangia cane.
The doctor defended his colleague despite the error — dog doesn't eat dog.
Journalism
I giornali non criticano mai gli altri giornali. Cane non mangia cane.
Newspapers never criticize other newspapers. Dog doesn't eat dog.