From sooth + say, or as a back-formation of soothsayer. Compare also soothsaw.
soothsay (third-person singular simple present soothsays, present participle soothsaying, simple past and past participle soothsaid)
- (intransitive) To foretell the future; make predictions.
soothsay (plural soothsays)
- Soothsaying; prediction; prognostication; prophecy.
- A portent; an omen.