Bałwan
Bałwan ; balvan/балван, bolvan/бoлван, archaism for "idol", is an ancient word common to all Slavic languages, describing a statuesque or monolithic depiction or a pillar or a plinth depicting or erected in honor of a deity. This object was worshipped or constituted a tangible representation of a cult image. The Western Slavs transcribed and pronounced the word as bałwan, which is its contemporary and old Polish lexical manifestation, whereas most Southern Slavs and the Eastern Slavs used the just slightly differently-vowelled bolvan.
In the Kyrgyz language of Central Asia, geographically remote from the territories Slavs are today identified with in Europe, balvan is a "strongman" or a hero, whereas in Persian, pahlevān denotes a militant or a veteran, as well as the plinth or boundary marker erected in his or her honor, or even a cairn, and, by extension, a fool. That latter meaning, at first secondary, became primary after Christianity was imposed on the Slavs, making bałwan acquire a distinctly pejorative primary meaning.
Some suggest that the Slavs share throughout their idioms such as they have evolved apart this single entity -- a common term for all cult objects in the form of a statue or cairn -- might suggest that idolatry spread early among the Slavic peoples, perhaps when they came in contact with Turkic peoples or Iranian. A word with similar etymology is the Slavic word for God or deity, bóg, a cognate of Sanskrit "bhaga"/Iranian or Persian bag. In India the concept of a deity or god is often relayed with the word bhagvan, variously transcribed as bhagwan.
A derived term from bałwan is the Polish word for idolatry: bałwochwalstwo.