Is "boom" related to the sound of walk? Is it something to do with hoof?

Native speaker’s answer
Rebecca
Yes! "Boom" is an onomatopoeia. An onomatopoeia is a word to describe a sound, such as an explosion or blast. In this context, "boom" is used to accompany her steps. He wants her to be able to walk sexily and feel a "boom" from every one of her steps. It does not have anything to do with the sound of hooves. It's all about her feeling confident and him being able to notice the impact of that confidence.