13 letters · 14 points in Scrabble
noun subtle and cumulative harmfulness (especially of a disease)
noun the quality of being designed to entrap
originEtymology tree English insidious Proto-Germanic *-inōną Proto-Indo-European *-dyé- Proto-Germanic *-atjaną Proto-Indo-European *-tus Proto-Germanic *-þuz Proto-Germanic *-assuz Proto-Germanic *-inassuz Proto-West Germanic *-nassī Old English -nes Middle English -nesse English -ness English insidiousness From insidious + -ness.
Etymology from Wiktionary, CC BY-SA 3.0