Hoy continues the Semitic consonant reconstructed as a plain h, and its cognates are the Hebrew heh, the Syriac he and the Arabic ha. What is unusual is not the letter but its position. Hebrew, Syriac and Arabic all inherit an order that begins aleph, beth, gimel, daleth, the sequence that gives the word alphabet its name and that still governs Hebrew letter numerals. Ge'ez begins hoy, lawe, hawt, may, and the traditional name of the order, halehame, is those first four sounds read as a word.
The two orders are not variants of one another. The halehame sequence is the South Semitic order, found in the Ancient South Arabian inscriptions from which the Ethiopian script descends, and an abecedary tablet recovered at Ugarit shows the same sequence already being written down in the second millennium BCE alongside the abjad one. Two families of alphabet therefore inherited not only a set of signs but a disagreement about the order to recite them in, and Ge'ez is the only script still in daily use that keeps the southern answer.
In the Northwest Semitic scripts the letter answering to hoy took on a second job, standing at the end of a word for a vowel that had no sign of its own. Ge'ez never needed that expedient, because from the fourth century it marked its vowels on the consonant itself. Here hoy is a consonant and nothing more.