I can find no indication of flower genera with the names 'emelita', or 'islip'.
Among references see J. Hutchinson, The Families of Flowering Plants.

More pertinently, there seems to be no reference to either of these names having ever been used as 'common' names for a flower species.

There has been previous discussion in other threads.

(Oleander, Nerium oleander, a Mediteranean species of the genus, was introduced to North America including Florida and southeastern states by Spanish settlers, ca. 1600s. (Ref. include Fox et al., 2005, IFAS Assessment of the status of non-native plants in Florida's natural areas, etc.). A common name for this plant is dogbane, although the plant is poisonous to all animals except a particular caterpillar. It is a shrub, growing to ca. 12 feet.)