according to Fabius and Aulus Gellius, is compounded of abs and temetum. “Temetum” was a strong, intoxicating drink, allied to the Greek methu (strong drink).
“Vinum prisca lingua temetum appellabant.”
—Aulus Gellius, x. 23.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894