It sounds pretentious, but I think it comes from having multiple ways to compare things for similarity. Using the word similarity says what you are using the a

It sounds pretentious, but I think it comes from having multiple ways to compare things for similarity. Using the word similarity says what you are using the angle for. Angle similarity might work just as well until someone comes up with another angle based calculation. Cosine Similarity becomes a specific meaning indicating how it's caclulated and why it's calculated. If you really wanted to be pretentious you could invent a Dimension Insensitive Euclidean Metric and call it DIEM to make it sound like you are putting some Latin into your papers.