I found a lot about this article interesting, but I think I can best explain where Shelfer's argument took my mind in a series of progressive observations:
- With the exception of Demosthenes, παράκλητος only appears in pagan literature six times, once in an Oxyrhynchus papyrus (P.Oxy. 2725.10), and in one piece of epigraphic evidence (a "confession inscription" from northeaster Lydia [modern Turkey]). Regardless whether or not we accept Shelfer's argument regarding παράκλητος as a Greek translation of the Latin advocatus, our Greek term appears to have been rare in gentile (pagan) usage.
- Despite this rarity among gentile writers, Shelfer notes that παράκλητος "is used often . . . by Jewish writers during the Roman Empire" (142). Philo alone, writing in the first-century CE from the northern Egyptian metropolis, Alexandria, uses the term eleven times. Given Philo's involvement in judicial affairs between the Alexandrian Jewish population and the Roman justice system, perhaps the utility of παράκλητος isn't all that surprising. At any rate, our term seems to be especially popular in Jewish Hellenistic Greek relative to gentile Hellenistic Greek. Παράκλητος even appears in transliteration in Hebrew and Aramaic texts as פרקליט [prqlyt]
- The Johannine writings continue the popularity of παράκλητος in Jewish texts: "The currency of the word in Jewish writings no doubt contributed to its most famous uses in the Christian Scriptures where it appears in two places, four times in a speech by Jesus to the disciples in the Gospel of John, the 'Farewell Discourse", and once in 1 John" (145). Five uses in a single set of texts (the Johannine literature) certainly qualifies as a frequent use of παράκλητος, a usage akin to Philo and distinct from gentile use.