I believe the letters of these two lines of code represent the letter combinations that will open two safe boxes.
Keyless combination locks were first introduced at the beginning of the 17th Century. During that period, and in literature, letter code combinations were written in capital letters followed by a period. In Beaumont and Fletcher's play The Noble Gentleman written before 1615 were the lines:
"A cap case for your linen, and your plate, with a strange lock that opens with A.M.E.N."
These two safe boxes make use of the rotary combination type of locks, using a combination dial to open it.
However, unlike the usual rotary combination locks, words, instead of numbers, surround these dials. The words surrounding the three dials of the first safe box are:
BERGERE PAS DE TENTATION QUE POUSSIN TENIERS GARDENT LE CLEF
PAX DCLXXXI PAR LE CROIX ET CE CHEVAL DE DIEU
J'ACHEVE CE DAEMON DE GARDIEN A MIDI POMMES BLEUES
The words surrounding the dial of the second safe box are:
A DAGOBERT II ROI ET A SION EST CE TRESOR ET IL EST LA MORT
These are of course the two hidden messages obtained after decoding the two parchments found by Berenger Sauniere. (See chapter 6 of this website).
The first safe box will open by positioning (and stopping) the three rotary dials on the following letters, moving the dials clockwise and then counter-clockwise repeatedly:
The final "V" from the word J’ACHEVE, should be selected twice in a row, moving the rotary dial clockwise, and then counter-clockwise. This is the reason why the final "V" in the Shugborough code does not have a period after it, since the same letter from the same word was chosen for the combination code:
