The town was probably named after a West Slavic (Lechitic) tribe called Leczanie, which inhabited central Poland in the early Middle Ages.
Some scholars however claim that the town was named after an Old Polish word łęg, which means a swampy plain.
In medieval Latin documents, Łęczyca is called Lonsin, Lucic, Lunciz, Lantsiza, Loncizia, Lonsitia and Lunchicia.
In the early 12th century, Gallus Anonymus called Łęczyca "Lucic", and in 1154, Arab geographer Muhammad al-Idrisi named it Nugrada, placing it among other main towns of the Kingdom of Poland, such as Kraków, Sieradz, Gniezno, Wrocław and Santok.
It received Magdeburg rights before 1267, and in 1331 the Teutonic Knights sacked the city during one of their repeated incursions into Poland.
The royal castle, built by Casimir the Great, was located on a small hill, protected by a moat with water from the Bzura river.
Gate tower was placed in the western wall, in the basement was a prison, and in the courtyard there was a two-storey tenement building.
Soon after its completion in the mid-14th century, the castle was named one of royal residences, and the seat of the Starosta of Łęczyca.
Furthermore, the castle served as headquarters of King Casimir IV Jagiellon, during the Thirteen Years' War (1454–66).
[5] Łęczyca was then occupied by Nazi Germany and incorporated into the region known as Reichsgau Wartheland[6] as part of the district (kreis) of Lentschütz (Germanized word for 'Łęczyca').
The Germans began to terrorize, pillage, and humiliate the Jewish population from the beginning of the occupation.
After 1305 part of the united Kingdom of Poland as a vassal duchy, later after 1343 incorporated by the king Casimir III the Great as the Łęczyca Voivodeship.