From BiblePortal Wikipedia

Hastings' Dictionary of the New Testament [1]

(Φιλόλογος, a Greek name, common among slaves and freedmen and frequently found in inscriptions of the Imperial household)

Philologus is the first of a group of five persons ‘and all the saints that are with them’ saluted by St. Paul in  Romans 16:15. Philologus is coupled with Julia (q.v._), and they may have been brother and sister or more probably husband and wife. If this be so, Philologus and Julia were perhaps the parents of ‘Nereus and his sister and Olympas,’ and this family were the nucleus of the Christian community which met under their leadership in their house (cf. the salutation to Prisca and Aquila, a married couple, ‘and the church that is in their house’ [vv. 3-5]; see, however, J. A. Robinson, Ephesians, 1909, p. 281). The relationship of Philologus to the persons mentioned also by name is, however, purely conjectural, as nothing further is known of any member of this group. Another group of five persons (none of whom are women) ‘and the brethren that are with them’ are saluted in the preceding verse, and it is reasonable to suppose that in each case the persons named were, by virtue of seniority as Christians, either leaders of a single ἐκκλησία, or heads (jointly if a married couple) of separate churches. The locality to which we shall suppose these churches belonged will depend upon whether we think the destination of these salutations was Rome or Ephesus.

T. B. Allworthy.

Fausset's Bible Dictionary [2]

 Romans 16:15. Saluted by Paul. Mentioned in the columbarium "of the freedmen of Livia Augusta" at Rome. Probably of the imperial household, as a Julia (An Imperial Name) is connected with him. He was the center of a knot of Christians.

Smith's Bible Dictionary [3]

Philol'ogus. A Christian at Rome, to whom St. Paul sends his salutation.  Romans 16:15.

Hastings' Dictionary of the Bible [4]

PHILOLOGUS . A Christian greeted in   Romans 16:15 .

Morrish Bible Dictionary [5]

A Christian at Rome to whom Paul sent salutations.  Romans 16:15 .

Holman Bible Dictionary [6]

 Romans 16:15

International Standard Bible Encyclopedia [7]

fi - lol´ṓ - gus ( Φιλόλογος , Philólogos , "fond of learning," "learned"): The name of a Roman Christian to whom Paul sent greetings (  Romans 16:15 ). His name is coupled with that of Julia, who was probably his wife or sister. Philologus and those united with him in this salutation formed by themselves one of the "house churches" or groups in the Christian community. The name is found in inscriptions connected with the imperial household, with reference to one of which Bishop Lightfoot has the following note: "It has been supposed that the name Philologus was given by the master to the freedman mentioned in this inscription, as being appropriate to his office (Friedlander I, 89, 160).... If so, some light is thrown on the probable occupation of the Philologus of Paul" ( Phil , 177, note 1).

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [8]

( Φιλόλογος ,Fond Of Talk), one of the Christians at Rome to whom Paul sent his salutations ( Romans 16:15). A.D. 55. Origen conjectures that he was the head of a Christian household which included the other persons named with him. Dorotheus makes him one of the seventy disciples, and alleges that he was placed by the apostle Andrew as bishop of Sinope, in Pontus (see Epiphanins, Mon. page 68, ed. Dressel). Pseudo-Hippolytus (De Lxx Apostolis) substantially repeats the same improbable tradition. His name is found in the Columbarium "of the freedmen of Livia Augusta" at Rome; which shows that there was a Philologus connected with the imperial household at the time when it included many Julias. The name Philologus was a common one at Rome (Lewin, Life and Epistles of St. Paul, 2:71).

Kitto's Popular Cyclopedia of Biblial Literature [9]

Philol´ogus, one of the Christians at Rome to whom Paul sent his salutations . Dorotheus makes him one of the seventy disciples, and alleges that he was placed by the apostle Andrew as bishop of Sinope, in Pontus. But this seems altogether improbable.