This paper examines the concept of ignorance across seven independent linguistic traditions: Chinese, Sanskrit, Hebrew, Greek, Latin, Persian, and Arabic. It analyzes both the etymological origins of primary terms and their classical or contemporary semantic boundaries relative to neighbouring concepts such as foolishness, unintentional error, and negligence. Key Findings: Indo-European Inheritance: In Sanskrit, Greek, Latin, and Persian, primary words for ignorance derive from a shared Proto-Indo-European verbal root (*ǵneh₃-, "to know") using a negating prefix, reflecting shared linguistic inheritance rather than a deliberate conceptual choice. The Semitic Boundary: Arabic lacks this Indo-European pattern, constructing an independent, highly layered semantic field via the Semitic triliteral root j-h-l (jahl, jāhiliyyah) and ghaflah. Value Reversal: Daoism in China (wúzhī) and Christian mysticism in Latin Europe (docta ignorantia) independently display a structural reversal of value, transforming ignorance from a flaw into a virtue. Significance: By moving beyond the dominant Greek-English framework, this study provides a broad comparative linguistic foundation for cross-cultural agnotology and historical semantics.