According to AncientScripts.com: Proto-Sinaitic, "Proto-Sinaitic, also known as Proto-Canaanite, was the first consonantal alphabet. Even a quick and cursory glance at its inventory of signs makes this script's Egyptian origin very apparent. Originally it was thought that at around 1700 BCE, Sinai was conquered by Egypt, and the local West-Semitic population was influenced by Egyptian culture and adopted a small number of hieroglyphic signs (about 30) to write their own language. However, recent discoveries in Egypt itself have compounded this scenario. Inscriptions dating to 1900 BCE written in what appears to be Proto-Sinaitic were found in Upper Egypt, and nearby Egyptian texts speak of the presence of Semitic-speaking people living in Egypt.
"No matter where and when the adoption of Egpytian signs onto a Semitic language occurred, the process of adoption is quite interesting. Egyptian hieroglyphs already have phonetic signs (in addition to logograms), but the Sinaitic people did not adopt these phonetic signs. Instead, they randomly chose pictorial Egyptian glyphs (like ox-head, house, etc), where each sign stood for a consonant. How did they decide which sign get which consonant? A sign is a picture of an object, and the first consonant of the word for this object becomes the sound the sign represents. In short, this is called the acrophonic principle.
"For example, the word for an ox is /'aleph/, which is the first
sign on the left Proto-Sinaitic column. It stood for the sound
/'/, which is the glottal stop (also written as /?/)."
During the Egyptian Middle Kingdom, foreign names, including Semitic
names, were written in characters of only one consonant, in other
words, alphabetically. This may have inspired the Semitic
adapter(s) (Sass). The style observed in the 1999 find in Wadi
el-Hol shows that the adoption took place around 2000 BCE, most likely
in Egypt itself. You can see examples of Proto-Sinaitic
inscriptions at Middle
Bronze Age Alphabets (WikiPedia) and The
Origins and Emergence of West Semitic Alphabetic Scripts .
The Proto-Sinaitic alphabet moved north and the Phoenicians
eventually adapted it by 1100 BCE. By then it had become more
stylized and simpler. The order, which basically has been
maintained to this day, was established by 1300 BCE. The reason
for the order is not known. It may simply be the order in which
the symbols were invented (Peter T. Daniels), or it may be based on an
Note that the Proto-Sinaitic and Phoenician alphabets only write
consonants, perhaps because the Egyptians had symbols for single
consonants but not vowels. The Greeks were to change this.