Dant writes a plain d and continues the Semitic consonant behind the Hebrew daleth, the Syriac dalath and the Arabic dal. The Northwest Semitic name means door. The Ge'ez name is not glossed in the tradition and no meaning is recorded for it here.
The letter is one member of a pattern that organises much of the Semitic consonant system. Sounds tend to come in threes: a voiced member, a voiceless member and an emphatic one. At the dental place that gives d, t and the emphatic t, which in Ge'ez is tayt. At the sibilants it gives z, s and the emphatic s of saday. At the velars it gives g, k and the emphatic k of qaf. The pattern is not perfect, and the labial series is the obvious gap, because Ge'ez inherited b but no p at all.
Reading the fidel with that pattern in mind makes the inventory look less like a list. Each of these letters has partners, the partners are predictable, and the places where a partner is missing or doubled are exactly the places where the interesting history is. The two p letters at the end of the order and the two emphatic sibilants in the middle of it are both such places.
English has nothing at the emphatic place, which is why transcriptions of the Semitic languages fall back on dots and underlines. A dot beneath a t in a scholarly transliteration of Ge'ez is not decoration. It is the whole difference between tawe and tayt, and dropping it, as popular writing usually does, makes two letters of the fidel indistinguishable on the page.