YouTube - Christians in Pompeii
First, let me warn you: this video was presented by an anonymous amateur Christian apologist who does NOT know that James Tabor and Simcha Jacobovici are, well, the flim-flam artists of the archaeological world. (yes, those two, of the Fishy Amphora Jar fame.)
Still, that should not necessarily detract from the findings.
There is a discussion of the Christianos graffito, which has faded into oblivion. Usually translated as: "Bovis listens to the Christians, cruel haters," the video cites Professor W. R. Newbold's interpretation that that which surrounds the word "Christianos" is transliterated Aramaic (Five Transliterated Aramaic Inscriptions). Jacobovici (ugh!) states the message is: "A strange mind has overtaken 'A', who is being held prisoner among the Christians."
Then the video discusses The House of the Baker. Among the items allegedly found therein are three graffiti and another evidence that the baker was Christian: a "Poinium Cherem," an apparent plastering over of a Priapean relief, a strange cross, and a Sator Square, matching another one in another part of town.
Well, James Tabor discusses the "Poinium Cherem," basically saying it was a curse graffito with the two stars being apotropaic: curse starswarding off some kind of evil. The words are supposed to be combined Greek and Aramaic meaning "Punish, blotting out:" in other words, smite completely. There is an independent discussion of this graffito at the Bryn Mawr Classical Review: unlike Tabor, the discussion indicates two words could just mean "flock" and "vineyard," respectively.
Next is the strange "cross." A very strange cross, indeed. The video editors do not give a reference of where it came from or even any independent citation that it actually WAS above oven, but they do show a book of inscription illustrations opened to the page where the cross was found. (6:00 in the vid) It is a very strange cross indeed. It is asymmetrical. The upright is shaped like a Club of Hercules  with the stout end at the bottom and the transverse appears to be some kind of skillfully crafted plank, crafted with more care than Romans would have carred to lavish on a condemned criminal IMO.
And of course, the old standby: the Sator Square. Whether it was originally Christian is anyone's guess. The square translates as: Arepo the sower holds the wheels with effort. Pretty innocuous, eh? But eventually the Christians figured out that the word "tenet" formed a cross  and that the whole thing was an amagram for a paternoster equilateral cross, with two A's and two O's left over. Alpha and Omega! Another such square, found on a column of a wrestling school in the town of Herculaneum, shows a fish symbol above the square.
Well it certainly looks like it's evidence for a toehold of Christianity in that small town. But what kind of Christianity??? It appears to have been not yet distinct from Judaism (except to regular Jews); it also appears to be also engaging in some kind of magic; and outsiders may have considered it to be a mind-control cult, perhaps a violent one.
And what conclusion may one draw from this for the development of the NT Canon? Were ANY of the NT books written at that date? And if so, did anyone in Pompeii know about it?
 An alternative New testament word for The Cross, Greek ξυλον, which in Latin is lignum, includes in the recognised meanings of the Greek word, "anything made of wood, as, cudgel, club, club of Hercules, an instrument of punishment, wooden collar, stocks, a combination of both [wooden collar and stocks] with holes for the neck, arms, and legs, gallows, stake on which criminals were impaled, a tree." (LSJ Greek-English Lexicon) The Latin meaning includes, "That which is made of wood, a writing-tablet, a plank, a spearshaft, a tree, a staff, a club." (Lewis & Short Latin Dictionary & Elementary Lewis Latin Dictionary)
 A tradition grew up in the ethiopian Coptic branch of Christianity that the five words in the Sator Square were the names of the five nails of The Cross! A more in-depth discussion by Duncan Fishwick, M.A., explains here:
[I]t is not until the sixteenth century that its efficacy as a cure for insanity and for fever is described in two early books, De Varia Quercus Historia, by Jean du Choul (Lyons 1555), and De Rerum Varietate, by Jérôme Cardan, a medical astrologer, (Milan 1557).
Perhaps the most extraordinary case related here is that of a citizen of Lyons who recovered from insanity after eating three crusts of bread, each inscribed with the magic square. This repast was punctuated by the recitation of five paternosters in remembrance of the five wounds of Christ and of the five nails of the Cross: Pro quinque vulneribus Christi, quae moriendo accepit, nee non pro clavibus. This local association of the square with the Lord’s Prayer and the nails may go back to the second century bishop of Lyons, St. Irenaeus, who himself had a devotion to the five ‘summits’ of the Cross: et ipse habitus crucis fines et summitates habet quinque, duas in longitudine et duas in latitudine et unam in medio in quo requiescit qui clavis affigitur. 9
In his Arithmologia (Rome 1665) R. P. Kircher relates that on a voyage to Abyssinia he had discovered that the Ethiopians invoke their Saviour by enumerating the five nails of the Cross, namely: SADOR, ALADOR, DANET, ADERA, RODAS – clearly the five words of the square in a corrupt form. A similar usage appears in a version from a tomb near Faras in Nubia where the five words follow a Coptic phrase which has been interpreted to mean “the names of the nails of Christ’s Cross.”10 In the eleventh century, on the other hand, the five words were used in Abyssinia to denote the five wounds of Christ. 11
9 Irenaeus adv. Haer. 2.24.4.
10 W. E. Crum, “Coptic Studies,” EEF (1897-1898) 63. cf J. Simon, AnalBoll 49 (1931) 165
11 H. Ludolf, Ad Historiam Arthiopicam Commentarius (Frankfurt a./M. 1695) 351.
Depictions of Christ on the cross first show only four or even two nails. later on in the Medieval period on they regularly show three nails. The fifth nail could have been, of course, the tree-nail of the typical cross which is also its fifth point at its center, GJohn's (19:34) mention of the use of a spear-shaft to inflict a wound notwithstanding.