Doc: In vino veritas.
Ringo: Age quod agis.
Doc: Credat Judaeus Apella, non ego.
Ringo: Iuventus stultorum magister.
Doc: In pace requiescat.
The literal meaning is
Doc: In wine there is truth.
Ringo: Do what you’re doing.
Doc: Let the Jew Apella believe it, not I.
Ringo: Youth is the teacher of fools.
Doc: Rest in peace.
This dialogue has a lot of subtlety whose sense I try to convey below.
- There’s truth in wine.
Along with being a gambler, Doc is a heavy drinker. Just prior, he said he hated Johnny because he reminded him of himself and later because Johnny is an educated man. Doc acknowledges that he is speaking more frankly than he otherwise might to a member of a criminal gang.
- Do what you’re doing.
Members of the Jesuit order use this Latin phrase to those undergoing Jesuit formation that they should focus intensely on their work. In English, we might say “Concentrate on the task at hand.” In the film, the task at hand was Doc’s drunkenness, hardly worthy of the high-minded admonition.
- Let the Jew Apella believe it, not I.
This is a quotation of Satires by the ancient poet Horace. In book one, satire five, people were trying to convince travelers that miracles were taking place at their shrines. Rather than a simple “I don’t believe you,” this phrase is utterly dismissive. In English, we might say it as “Go tell someone who will believe it.” Doc is likewise brushing off Johnny.
- Youth is the teacher of fools.
Johnny is the younger of the two, but with this line and by tapping his pistols, he implies that Doc is the inexperienced one unaware of the danger he’s flirting with. Johnny could have conveyed similar meaning with “Don’t bite off more than you can chew, boy.”
- Rest in peace.
This phrase is a common fixture of grave markers with which Doc warns that Johnny should beware the danger at hand and foreshadows the showdown between Doc and Johnny later in the film.