Why is the rooster the national animal of France?

The Latin word "Gallus" means both "Gallic, related to Gaulish people" and "rooster". Some antique coins were marked by a rooster, but the bird wasn't at the time an emblem for Gaulish tribes.

In the Middle Ages the rooster is a religious symbol, due to the Good Book story. This is why it is nowadays, still standard to find a rooster on most churches.
In the Renaissance era the rooster is progressively associated with the emerging national idea. Under the Valois and Bourbons dynasties, the king's effigy is often associated with the bird on medals and coins. The rooster is a minor emblem, but is present in the Louvre and Versailles.

The revolutionaries in search of emblems adopt it as a symbol of the national identity.
After 1830 by Decree of the king Louis-Philippe, the rooster adorns the flag of the National Guard.

After WWI, the Elysée palace has a grille decorated with the rooster, the 'grille du coq', still in place today . During WWI, propaganda posters and newpapers caricatures consecrate the rooster as an allegory of French courage. The reference to Gaulish tribes fighting against the Romans add a romantic flavour to the symbol. The rooster is the symbol of France as a country with peasant origins, proud, determined, courageous and fecond.