An abecedarium is an alphabet table. I ran across this in the Artifact column of Archaeology (March/April 2016):
The first alphabetic writing system was created in the Levant and Sinai Peninsula sometime in the second millennium B.C., probably between 1850 and 1700 B.C., by adapting Egyptian hieroglyphs—a writing system expressing both concept and sound—to represent only sound. This Proto-Sinaitic alphabet is the ancestor of many of the writing systems that developed across the world. Until now, the earliest known alphabet tables, called abecedaries, have been found on cuneiform tablets from Ugarit, in what is now Syria, dating to the thirteenth century b.c. But while studying an undeciphered ostracon found in a tomb at Luxor, Egyptologist Ben Haring of the University of Leiden discovered an abecedary that predates those tablets by two centuries, making it the oldest example ever found.
Is the (anonymous) author suggesting the creators were creating phonetics? Or is this something else?