Because the crowing of a cock once prevented our Saxon ancestors from
massacreing their conquerors, another part of our ancestors, the
Danes, on the morning of a Shrove Tuesday, while asleep in their beds.

This is the account generally received, although two lines in an
epigram "On a Cock at Rochester," by the witty Sir Charles Sedley,
imply that the cock suffered this annual barbarity by way of
punishment for St. Peter's crime, in denying his Lord and Master--

"Mayst thou be punish'd for St. Peter's crime,
And on Shove Tuesday perish in thy prime."

A writer in the _Gentleman's Magazine_ also says--"The barbarous
practice of throwing at a cock tied to a stake on Shrovetide, I think
I have read, has an allusion to the indignities offered by the Jews to
the Saviour of the World before his crucifixion."--_Ellis's Notes to
Brand._

Why was cock-fighting a popular sport in Greece?

Because of its origin from the Athenians, on the following occasion:
When Themistocles was marching his army against the Persians, he, by
the way, espying two cocks fighting, caused his army to halt, and
addressed them as follows--"Behold! these do not fight for their
household gods, for the monuments of their ancestors, nor for glory,
nor for liberty, nor for the safety of their children, but only
because the one will not give way to the other."--This so encouraged
the Grecians, that they fought strenuously, and obtained the victory
over the Persians; upon which, cock-fighting was, by a particular law,