dense (adj.)youdaoicibaDictYouDict[dense 词源字典]
early 15c., from Middle French dense and directly from Latin densus "thick, crowded; cloudy," perhaps from PIE root *dens- "dense, thick" (cognates: Greek dasus "hairy, shaggy"). Sense of "stupid" is first recorded 1822.[dense etymology, dense origin, 英语词源]