In Breishit 39:6 it says that Potiphar did not pay attention to anything that Yosef handled "except for the bread that he (Potiphar) eats."
"וַיַּעֲזֹב כָּל־אֲשֶׁר־לוֹ בְּיַד־יוֹסֵף וְלֹא־יָדַע אִתּוֹ מְאוּמָה כִּי אִם־הַלֶּחֶם אֲשֶׁר־הוּא אוֹכֵל וכו'׃
Rash"i explains that here lechem is a "clean language version" for "wife". I read Siftei Chachamim's explanation on Rash"i, and I'm still puzzled as to why Rash"i doesn't go with the literal meaning that it means "bread" (or "food").
First - What would it mean to "eat" someone's wife? I.e. - if Rash"i is stating that the Torah used "Lashon Naki", he's implying that the other way is not "naki". But, "eating" one's wife doesn't sound like it means anything at all. How does Rash"i state that it's not "naki". And even if it weren't, how does Rash"i know that it means "wife"? It could be anything.
Second - Why couldn't it mean "bread"? After all, we see that when Yosef's brothers arrived and Yosef invites them to eat at his home, the Torah states that the Egyptians wouldn't eat bread with the Hebrews. Potiphar clearly knew that Yosef was a Hebrew and he wouldn't want Yosef touching his bread. So, why not go by the literal translation esp. where there is clear support for the idea?