Cf. delta 148, delta 151, delta 302, delta 305, and epsilon 200.
Properly, the perfect of the verb "fear" should have o-grade in the singular, as *dedwoya which gives δείδω or δέδοικα (with k inserted by analogy with other perfects). The zero-grade should appear in the plural, as δέδιμεν etc. But a great variety of forms are attested: see LSJ under δείδω .