from
Easton's 1897 Bible Dictionary
Gallio
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).