From "Korean Art Collection in the Brooklyn Museum" catalogue:
The long fine slender neck and the small spout on the broad
shoulder are typical characteristics of Goryeo kundika (Buddhist
ritual ewer). Kundika were used to offer clean water to the
altar or carried by Buddhist monks traveling for cultivation.
This kundika type was popular during the Tang Dynasty and
continued to be used in the northern regions of China during the
Northern Song and Liao dynasties. In Goryeo, bronze kundika were
especially popular. Similar examples were also made in celadon.
The shoulder of [this] kundika is decorated with incised lines,
and the spout was cast separately and attached to the shoulder.
The lid, which was attached to the spout by a hinge, has been
lost. The particularly thin and elongated profile of the kundika
suggests a date of the twelfth or thirteenth century.