This is from an etymology dictionary.Originally Posted by chaika
1567 (implied in alphabetical), from L.L. alphabetum (Tertullian), from Gk. alphabetos, from alpha + beta, the first two letters of it, from Heb.-Phoen. aleph, pausal form of eleph "ox" + beth, lit. "house;" the letters so called because their shapes resembled or represented those objects. The Greeks added -a to the end of many Heb.-Phoenician letter names because Gk. words cannot end in most consonants.