Synonyms for Bluebonnet (same or very similar meaning)
WordNet sense 1 (low-growing annual herb of southwestern United States (Texas) having silky foliage and blue flowers; a leading cause of livestock poisoning in the southwestern United States):
buffalo clover, Texas bluebonnet, Lupinus subcarnosusWordNet sense 2 (a brimless dark blue Scottish cap with a flat top and a plume on one side):
balmoralFrom the ODE community, based on WordNetadd/edit