The second word: buenos días – good morning.
You are out for an early morning walk, the sun is rising, the birds are whistling, dew is lying on the field. Somebody comes towards you and you wish them a good morning. He is holding a book, and inside there are photos of elephants – slides, to be precise, the kind that used to be projected onto a wall. Because he took them long ago he is feeling nostalgic (buenos), and the photos are indeed slides (días).