False cognate
Some years ago, I had the opportunity to spend a summer studying Spanish at La Universidad Católica in Quito, Ecuador as part of my undergraduate program. Although I had studied French all through high school and my first year of college, I switched to Spanish after passing a foreign language proficiency graduation requirement in French. I studied Spanish for two semesters and then I was off to Quito to squeeze a year of Intermediate Spanish into two months. I had the good fortune to live with a warm and welcoming Ecuadorian family in a comfortable home a short bus ride away from the university. They made my roommate and I feel very welcome.
My twentieth birthday happened to fall during the first week I was there. My host mother was kind enough to have a special treat at lunch that day, and her three adult children along with their spouses, her husband, the maid and my roommate all sang to me. When they finished, I said, "Mil gracias. Estoy embarazada." The smiles were wiped from all the heretofore friendly faces and you could have heard a pin drop.
Fortunately, one of her children spoke enough English to know that I had a near-perfect accent but seriously imperfect vocabulary: "embarazada" did not mean "embarrassed" as I thought, but rather "pregnant." She clarified what I said (to me) versus what I meant to say (to them), and all was well...although after that my host mother insisted I go to church with her every Sunday and seemed to watch my waistline rather closely for the rest of my stay.