Ggtkuk

Here is a very old (possibly 2nd century) depiction of the Crucifixion of Jesus on an engraved gem:

What do the words say?

Source: https://en.wikipedia.org/wiki/Crucifixion_in_the_arts#Late_Antiquity

The words are Greek:

ΟΡΦΕΟϹ ΒΑΚΚΙΚΟϹ

Orpheos Baccicos

My guess is that it was meant to be Orpheus Bacchicos, either misspelled or written in a different dialect. In this case, it would mean "Bacchic Orpheus" (where "Bacchic" refers to the worship of Bacchus, and "Orpheus" is the singer who went down to the Underworld and returned).

Both Bacchus and Orpheus had cults relating to death and resurrection, and they were sometimes unified into a single deity called "Zagreus", so I wouldn't be too surprised to see their names associated with the Christian idea of the Resurrection.

According to this site, it has the image of

a crucified man identified as ΟΡΦΕΩΣ ΒΑΚΧΙΚΟΣ (Orpheos Bacchikos).

A dedicated scientific article analysing the stone (in relation to, for instance, the Crucifixion of Jesus) can be found here. Notice that it is unclear if the image is that of Jesus. Orpheos might be a reference to the Greek legendary figure of that name. For instance, the article states:

The fact
that Christ appears represented on a cross, but is designated OPΦEOC BAKKIKOC—“Bacchic
Orpheus”—, is of remarkable singularity in religious history, because Christ has taken the
place of Orpheus, and not vice versa, as it is well-known from catacomb frescoes, for
example with Orpheus as the Good Shepherd. Therefore the artefact would be
syncretistic or Orphic, however with an Orpheus subjected to Dionysian suffering like Marsyas at the stake, and not like the Apollonian Orpheus with his lyra amidst tamed beasts. Bakkikos as an epithet of Orpheos is not tautologic, because beside the tradition that (as it seems to be the case here) Orpheus was killed by the enemies of his own following, there was among many others one famous variant, in which Orpheus, after returning from the Hades, abandoned his earlier habit of worshipping Dionysus-Bacchus and turned to Helios-Apollo instead, for which the insulted god had him dismembered by his Maenads. Therefore the designation Bakkikos would contrast this Orpheus on the
cross from the follower of Apollo and identify him as the founder of the Dionysian
Mysteries (see below).