sentences:  In the early Piast period, a fortified settlement existed nearby the present-day town and the area formed part of the Lubusz castellany within the Kingdom of Poland until the mid-13th century.Ośno Lubuskie was mentioned for the first time in 1252, in Latin, as "civitas forensi Osna".The name is of Slavic origin and is derived from the word "osa"/"osina".