What is "olelkovich"

The Olelkovich family was a 15th–16th-century noble family from the Grand Duchy of Lithuania. Their main possession was the Duchy of Slutsk–Kapyl; therefore, they are sometimes known as Slutskys. They hailed from the Lithuanian Gediminids (male line) and Russian Rurikids (female line). According to the 1528 military census, the family was the fourth wealthiest magnate family in the Grand Duchy. However, its influence declined after the Union of Lublin (1569). The last member of the family was Sophia Olelkovich Radziwill (1585–1612), wife of Janusz Radziwiłł and saint of the Eastern Orthodox Church. After her death, considerable wealth and the Duchy of Slutsk passed to the Radziwiłł family.