what other fingers have been used a gesture in the clasic era?
The middle finger.
The finger
The middle finger gesture was used in ancient times as a symbol of sexual intercourse, in a manner meant to degrade, intimidate and threaten the individual receiving the gesture. It also represented the phallus, with the fingers next to the middle finger representing testicles; from its close association, the gesture may have assumed apotropaic potency. In the 1st-century Mediterranean world, extending the "finger" was one of many methods used to divert the ever-present threat of the evil eye.

what does it mean to flip someone off with your thumb out UNANSWERABLE
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The finger [SEP] Classical era
The poet Martial has a character in good health extend "the indecent one" toward three doctors. In another epigram, Martial wrote: "Laugh loud, Sextillus, at whoever calls you a "cinaedus" and extend your middle finger." Juvenal, through synecdoche, has the "middle nail" cocked at threatening Fortuna. The indecent finger features again in a mocking context in the "Priapeia", a collection of poems relating to the phallic god Priapus. In Late Antiquity, the term "shameless finger" is explained in the "Etymologiae" of Isidore of Seville with reference to its frequent use when accusing someone of a "shameful action".