In Argentina, my husband’s home country, they have a street language called Lunfardo and there is an influence of several Native American languages in different areas. Where my husband’s parents came from the predominant Native American tongue was Guarani. He can, of course, speak perfect Spanish, but when he would speak with his mother they used so much Lunfardo and Guarani that other Spanish-speakers could not understand them!
As I was trying to learn Spanish, I would pick up a phrase or two from him, thinking it was Spanish, and repeat it to my adopted daughter from Honduras. She would look at me like I was nuts. What I learned was not Spanish at all but Lundardo or Guarani. One phrase was Tengo fiaca. Tengo is Spanish for I have but fiaca is Lunfardo and it means laziness. In English, Tengo fiaca would be I feel lazy. My daughter had no idea what I was trying to say!
I actually can pick up Guarani easier than Spanish. I think the French I studied in my youth gets all scrambled with Spanish. But, Guarani sounds like nothing else and it is easier for me to remember. I only know phrases and can’t really form my own sentences. In our house, most swearing is done in Guarani, thanks to my husband’s tutelage!