King James Bible Dictionary

The elder brother of Seneca the philosopher, who was tutor and for some time minister of the emperor Nero. He was "deputy", i.e., proconsul, as in Revised Version, of Achaia, under the emperor Claudius, when Paul visited Corinth (Acts 18:12). The word used here by Luke in describing the rank of Gallio shows his accuracy. Achaia was a senatorial province under Claudius, and the governor of such a province was called a "proconsul." He is spoken of by his contemporaries as "sweet Gallio," and is described as a most popular and affectionate man. When the Jews brought Paul before his tribunal on the charge of persuading "men to worship God contrary to the law" (18:13), he refused to listen to them, and "drave them from the judgment seat" (18:16).

who sucks, or lives on milk

Proconsul of Achaia, dismisses complaint of Jews against Paul.
Acts 18:12-17

(one who lives on milk), Junius Ann'us Gallio, the Roman proconsul of Achaia when St. Paul was at Corinth, A.D. 53, under the emperor Claudius. (Acts 18:12) He was brother to Lucius Ann'us Seneca, the philosopher. Jerome in the Chronicle of Eusebius says that he committed suicide in 65 A.D. Winer thinks he was put to death by Nero.

GALLIOT

GAL'LIPOT, noun A small pot or vessel painted and glazed, used by druggists and apothecaries for containing medicines.