Webster's Revised Unabridged Dictionary
LL. sacramentarium,: cf. F. sacramentaire,
Chambers's Twentieth Century Dictionary
L. sacramentum, a sacred thing—sacrāre, to consecrate—sacer, sacred.
It is inserted in the ancient sacramentary of Pope Gelasius (A.D. 495).
"The Ceremonies of the Holy-Week at Rome" by Charles Michael Baggs
This rite is found in the Gelasian, Gregorian and other sacramentaries.
"Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 5" by Various
An Elegy for the Sacramentary.