The term alphabetical usually describes a list where the terms are arranged by their first letter's position in the English alphabet.
The term alphabet comes from the latin Alphabetum, which comes from the Greek Alphabetos. Alpha and Beta are the first two letters of the Greek alphabet, and thus when we refer to something as alphabetical, we refer to it's similiarity in organization to the sequence of the first and second letters of the Greek alphabet.
Am I the only one wondering where some words come from? If you have a word for me, comment below.