This Mermaid is the symbol and armoury of Warsaw, the Polish capital.
There is a legend named "The Legend of the Warsaw Mermaid"..
Do you have the time to read it?

Once upon a time there were two mermaid sisters who swam
to the shore of the Baltic Sea from their home deep in the sea.
They were very beautiful.

One day they both decided to come ashore.
The first sister headed up to the Danish straits
where she sat down at the entrance to the port of Copenhagen
and she remains there to this very day.

The other sister swam first to the port of Gdansk,
from where she decided to swim the river Vistula.
She came out of the water onto the sandy bank
to rest on the foot of what is today Warsaw's Old Town.
She loved the place so much that she decided to stay.

The fishermen living in this area noticed that
during their fishing someone was churning the waves
of the Vistula River, tangling the nets and releasing the fish.

The mermaid enchanted them with her beautiful singing,
and they did not harm her.

One day a wealthy merchant saw the mermaid
and heard her lovely song. He quickly calculated
how much money he could make displaying her at market fairs,
so he captured her and imprisoned her in a wooden shed
without any water. Her cries for help were so loud
that soon a young fisherman's son heard her,
and with the help of friends he set her free at night.

Grateful that the town's people had defended her,
the mermaid promised to help them in time of danger.
This is why the Warsaw Mermaid is armed:
She bears a sword and a shield to defend the city.