Engañar is the common Spanish word meaning “to deceive”, and is especially common in its meaning of “to cheat on [a spouse or girl/boyfriend].”
But who would have thought its related to the English ingenuous?
Both are, after all, forms of naïveté.
Both come from the Latin root gen-, meaning “to produce”. Think, genesis. After all, in the beginning, everything and everyone was naive.
Via the Greek parallels and Latin descendants, we get a myriad of modern words, including: genus and genius. There is a certain genius in deceiving. Of course.