Authors of language textbooks (especially, those aimed at advanced-level students) realize that it is necessary to include cultural content in a textbook to make it useful. However, they are often prevented by their annoying prissiness from addressing said content in a direct and honest way. To give an example, today in my Advanced Spanish Conversation class we read a text by a Mexican author where words "pendejo" and "huevona" were used. The prissy authors of the textbook translated the word "pendejo" as "dumb" and the word "huevona" as "lazy." This, of course, made my Mexican students laugh hysterically.
The words in question can, on certain occasionas, be used in the sense suggested by the book's authors. However, the set of implications they carry is very offensive, especially in Mexico where bandying around "pendejos" and "huevones" at every opportunity might get you into serious trouble. I mentioned that to my students and warned them to be very careful with this vocabulary. I didn't go into details of what these words actually mean, but I will do so for the benefit of my blog readers. Be forewarned, though, that the etymology of these words, just like many words in the Spanish vocabulary, is not for the faint of heart.
Pendejo - the original meaning of this word is "a particle of dirt that hangs from one's pubic hair." That particle of dirt is obviously neither good nor useful, so referring with this word to a person is quite offensive.
Huevón - originally referred to bulls who were not castrated and, therefore, still had balls (one of the meanings of "huevos" is testicles.) These bulls were used for breeding instead of hard work. This is why the word is often used to refer to a lazy person.
I do wish authors of language textbooks had enough courage to avoid bowdlerizing an entire language simply because it hurts their sensibilities to accept cultural and linguistic variations.