Vatican II very sensibly suggested that the old Breviary collection could be enriched by rescuing other hymns from the treasury of the Western Church. Happily, a gorgeous composition by S Peter Damian (d1072) was found for the Festum of S John the Evangelist: Virginis virgo venerande custos, in the Sapphic metre (I wonder what the dear old girl would have made of it if she could have known how much Christian Latins would make enthusiastic use of her metrical innovation). The bad news: Dom Anselmo Lentini and his merry men decided to Correct it.
Starting even before the Carolingian Renaissance, Latin writers and especially hymnographers, often when they wanted an effect of majesty and grandeur, reached for the Greek language. So, after the first line with its alliterative wordplay (O venerable virgin guardian of the Virgin) S Peter went one better in his second line: magnus aeterni logotheta Verbi. Given a pedestrian translation, this would be 'Great wordplacer of the eternal Word', where the Greek neologism logotheta hits you, in all its quadrisyllabic sonority, immediately after the caesura. It plays with the Johannine description of our Lord as the Word, the Logos, Verbum, and a suggestion of assonance in aeterni ... logotheta. But whereas in the first line, with its "Virginis ... virgo", the Saint uses the same Latin word but changes the case ('anaphora with polyptoton'; an elegance particularly associated with the 'hellenistic' poets), in the second line he achieves an elegant variatio by creating a Greek compound containing logos to match his Latin Verbi.
The post-Conciliar Revisers detested any sort of fun with words; in their austere schoolmasterly comments there are few stricter see-me-afterwardses than nimius lusus verborum. Here they call in aid the principle of 'graecismum nunc insuetum'. And Dom Anselmo claims to find the nominative 'magnus' (instead of the vocative 'magne') unacceptable: naughty Anselmo; he must have known perfectly well that this little problem, if problem it is*, could have been corrected by "magne et".
So what did the revisers write? 'praeco qui Verbi coleris fidelis'.
Oh dear. (But to be fair, Lentini was himself a Latin poet of no mean ability, and did his best with the assonance 'praeco ... coleris'.)
*Nominatives in place of vocatives seem to be no problem in the Gloria in excelsis Deo.