Christianity in the roman empire.

[Urselius]

The Chi-Rho symbol was used by pagan Greek scribes (pre- and post- Incarnation) to mark, in the margin, a particularly valuable or relevant passage; the combined letters Chi and Rho standing for ''chr?ston,'' meaning "good." Grant, Michael (1993), The Emperor Constantine, London. ISBN 0-75380-5286 p. 142.