The name ''Rus'' is often conflated with its Latin forms ''Russia'' and ''Ruthenia'', thus Belarus is often referred to as ''White Russia'' or ''White Ruthenia''. The name first appeared in German and Latin medieval literature; the chronicles of Jan of Czarnków mention the imprisonment of Lithuanian grand duke Jogaila and his mother at "" in 1381. The first known use of ''White Russia'' to refer to Belarus was in the late-16th century by Englishman Sir Jerome Horsey, who was known for his close contacts with the Russian Royal Court. During the 17th century, the Russian tsars used ''White Rus'' to describe the lands added from the Grand Duchy of Lithuania.