Drużno (Polish: Jezioro Druzno; German: Drausensee, Lithuanian: Drūsuo) is a body of water historically considered a lake in northern Poland on the east side of the Vistula delta, near the city of Elbląg.

As it is currently not deep enough to qualify as a lake hydrologically and receives some periodic inflow of sea water from the Vistula Lagoon along the Elbląg River, some suggest that it be termed an estuary reservoir.

The German name Drausensee, in earlier records called Drusensee, is connected to the ancient trade city of Truso, which stood within the lands now occupied by Elbląg.

It lies to the east of the Nogat, the main right branch of the lower Vistula, at the edge of the lowland of the delta (Żuławy Wiślane), which is a region of shifting sediments and channels partly controlled by dikes, dams and ditches.

When there is a strong wind blowing to the south the bay can be a meter or so higher than the lake, which causes back currents in the river.

It should have sedimented over long ago but the high throughput of water from various sources brings fresh Oxygen into the lake, retarding its aging.

The total capacity is about 22.4 million cubic metres (18,200 acre⋅ft) with a catchment area of 1,084 square kilometres (419 sq mi).

[citation needed] When the lake became useless for that purpose Elblag was still a port with access to the Zalew Wislany and through there to the Gulf of Danzig.

In an attempt to make the inland region more accessible, the Prussian government opened the Elbląg Canal through the lake in 1860.

Instead the entire route has been converted into a recreational area featuring nature preserves such as Lake Druzno.

Janow Pomorski was after 1945 the name of the village of Hansdorf about 7 km to the southeast of Elbing (now Elbląg) where the traces of some workshops have been found that were on the then edge of the lake.

Truso might well have been at Janów Pomorski, but the artifacts give no indication that the native populations were Prussian, Slavic or Scandinavian.

Moreover, Adalbert of Prague, who came with Boleslaw Chrobrie's soldiers, had been beheaded further north-east at the coast of the Baltic Sea near (Fischhausen), now Rybaki, for cutting down the sacred groves of the Old Prussians as part of an effort to conquer them under guise to convert them in (997 AD).

Ptolemy,[2] writing in the period of the initial lake, refers to the entire Gulf of Gdańsk as Venedicus Bay and states that the Greater Venedae occupied its coast.

Wulfstan of Hedeby left an account of a voyage dated to about 880 AD as told to Alfred the Great and inserted into his translation of Orosius' Histories.

Wulfstan sailed from Hedeby (Haithabu), Jutland to Truso in seven days keeping Weonodland ("Wendland") on the right as far as the mouth of the Weissel (Vistula).

As the greater Venedi and the Weonods cannot have spoken the same language the name must once have applied to both Balts and Slavs (unless Ptolemy was wrong).

Some Gotini (Goths) and Aelvaeones (Elbingers?, local name is to this day Albinger) dwell on the lower Vistula.

Proto-Slavic began to differentiate after the Slavs expanded beyond their Carpathian homeland in the 6th century AD, too late for the foundation of Truso.

On the right bank of the Vistula the Proto-Baltic speakers had been gradually giving ground to the Proto-Slavs in the east and lost Pomerania to Germanic expansion.

The different duchies made hypocritical claims to lands they never controlled and invited the Teutonic Order to suppress "rebellions" there.

It is possible therefore that the Kashubian Duchy of Gdańsk was asserting a nominal claim over Lake Drużno and Truso, but it was never one recognized by the Old Prussians.

The name of the settlement has been restored in Old Prussian by prominent worldwide acknowledged Balticists, on the basis of Wulfstan's German (t/d), as *Drūsā - cf.

Druso first by Georg Gerullis (Die altpreußischen Ortsnamen, Berlin 1922, 187), and recently - by Vytautas Maziulis (Prūsu kalbos etimologijos zodynas I, Vilnius 1988, 231).

Such a restoration shows the continuity of Western Baltic on this territory in course of several hundred years, probably even before the attested Truso, which is the first known settlement name in the coastal region.

The possible originating cultures are not diminished by this restoration, but the linguistic evidence points to the presence of Balts on this territory.

On the other hand, the historical linguist Julius Pokorny, whose conjectures are strongly outdated at least in the field of the Baltic linguistics, lists *trus-, "reed", as an Indo-European root, not used in English, but appearing in Old Church Slavonic and Lithuanian words from a Balto-Slavic form *trusom.

Recently excavations near Gut Hansdorf (now Janowo) were resumed by Polish authorities and the site of 20 hectares (49 acres) unearthed.