The heraldic blazon reads: Gules, on a bend or, a bear passant sable, langued, armed and vilené of the field.
The founding legend has it that Duke Berthold V of Zähringen vowed to choose as namesake the first animal his hunt met in the wood that was to be chopped down for the new city.
Then, as Konrad Justinger's chronicle puts it: The bear motif is in evidence as early as 1224 (on city seals), and has remained in use ever since.
As long as Bern still considered itself (at least formally) to be part of the Holy Roman Empire, subject to the Emperor, this was reflected in its coat of arms.
The imperial eagle was placed above the Bernese shield, constituting a compound coat of arms known as the Bern-Rych, or "Berne-Empire".
Eventually, Bern formally gained the full sovereignty it had long since de facto possessed with the Peace of Westphalia in 1648, but it was not until 1700 that the eagle was replaced with the Republic's trefoil crown that signified ultimate temporal power.