Eliezer is the servant Abraham arms in Genesis 14:14, where the text says he led 318 trained men; the Rabbis read the number as the value of Eliezer's own name, so that Abraham went out with one man — his servant — and the verse's arithmetic says so. It is the gematria every account of the method begins with, and the one that shows the practice in the Talmud's own hands rather than in the Kabbalists'.