The sutra is named the Lotus Sutra because the lotus symbolized the oneness of cause and effect, specifically the cause of aspiring to enlightenment (Buddhahood) and the effect of attaining it, since the lotus is a flower that blooms and seeds at the same time. It also symbolizes the purity of Buddhahood, blooming in the midst of our ordinary lives just as the lotus blossoms in muddy pond water.
Shakyamuni Buddha himself is in actuality the Eternal Buddha who is always present in our lives, leading us to the realization of our own innate Buddhahood.