insidious

Where does the word "insidious" come from? It comes from Latin sedere, passing through Latin before entering English (1530s).

Insidious’s story begins in Latin: sedere meant “to sit.” To sit, giving rise to insidere (to sit in wait, to lie in ambush). Within Latin, it grew into insidiosus by ancient. Lying in wait, deceitful, from insidiae (an ambush, from insidere). It reached English by 1530s as insidious. Settled as the English word for something proceeding harmfully but gradually or subtly. Today, insidious means proceeding in a harmful way that is gradual, subtle, and hard to notice.

1. Stage 1 · Latin · ancient sedere "to sit", to sit, giving rise to insidere (to sit in wait, to lie in ambush).
2. Stage 2 · Latin · ancient insidiosus "lying in wait, deceitful", lying in wait, deceitful, from insidiae (an ambush, from insidere).
3. Stage 3 · English · 1530s insidious "proceeding harmfully but gradually or subtly", settled as the English word for something proceeding harmfully but gradually or subtly.