Postpositives
There are many words in Latin which are used as a kind of "verbal punctuation." Because they do not convey meaning on their own, they are not used as the first word of the sentence, but they very often appear in second place. This is why they are called postpositives - they are placed after (post) the beginning of the sentence.
Sometimes they are not exactly the second "word" of the sentence, because sometimes we write out as individual words a phrase that was pronounced as if it were a single word. You can tell if a phrase must have been pronounced as if it were a single word based on how the postpositive comes after it!