I think the word you are hearing is "seg selv" i didnt actually hear it in this video but its a sound i hear commonly in norwegian. "selv" is like "self" in english. It is paired with a person just like english, for example: myself, yourself, themselves, itself ..etc. Seg selv = itself. If this isn't what you mean, perhaps you mean in this video, another possibility is the word "si" =say (english). because this video is about words you can "Say" the word "Si" was used many times and may sound like a longer word when it blends into the words around it as she speaks at a fluent pace.