Is it ensure, insure, or assure?
small North American flycatcher, pewit, 1700, phebe, so called in imitation of its cry; spelling altered (1839) by influence of the woman's proper name Phoebe.
fem. proper name, late 14c., originally a name of Artemis as the goddess of the moon, from Latin Phoebe, from Greek phoibos "bright, pure," of unknown origin. The fem. form of Phoebus, an epithet of Apollo as sun-god.
Five or the point of five (1940s+ Crapshooting)