In the American version of The Killing, detective Stephen Holder is seen using the term habibi several times when talking to his sister and his nephew, Habibi is an Arabic term of endearment widely used with close family members and friends. From what I can tell, Holder doesn't seem to have any Arab roots, so why the seemingly random use of that term?
I believe it's because Holder is supposed to embody the addict/cool/street guy. He is the guy that knows how to get secrets out of people and how to get things done discretely. Basically he is a smooth talker! So it makes sense that he would know a few words of a different language.
Also I don't see why he can't also have a knowledge of various languages! It's upsetting that would bother someone. I'm pretty sure there were a few episodes that featured Arabic speaking in regards to the mosque and the high school teacher.
Let's all not forget that Holder was an avid book reader, and general seeker of knowledge. He is interested in many cultures, and draws from many religions...
ALL WHILE HE IS TEACHING HIMSELF
So he might not be getting the exact details right, although he is getting the general messages from the teachings, and applying them to his own life.
I personally do not know any Arabic, so I can't weigh in on if the term was used correctly or not within the context.
I just thought it was important to point out that even if he is a white male with no ties to any ethnic cultures/ religions, it does not mean that he isn't knowledgeable about them.