I am interested in the development of the word sacramentum, from the classical to the current ecclesiastical usage. The Lewis & Short entry lists the following meanings:
A. Jurid. t. t., the sum which the two parties to a suit at first deposited, but afterwards became bound for, with the tresviri capitales; so called because the sum deposited by the losing party was used for religious purposes, esp. for the sacra publica; v. Fest. p. 344 Müll.; or, perh. more correctly, because the money was deposited in a sacred place;
B. Milit. t. t. (cf. infra, 2, the passage from Cic. Off. 1, 11, 36), orig. the preliminary engagement entered into by newly-enlisted troops (this was followed by the proper military oath, jusjurandum, which was at first voluntary, but, after the second Punic war, was demanded by the military tribune):
II. In eccl. and late Lat., something to be kept sacred.
In current (Catholic) Ecclesiastical Latin, the word has a precise meaning: one of the seven sacraments.
In the Vulgate and Patristic Latin, though, this term has many usages, many of which are detailed in the L&S entry under meaning (II). St. Paul, Augustine, and Hilary (of Poitiers), e.g., use the term almost interchangeably with the Greek loan-word mysterium.
If possible, I would like a brief overview of the evolution of the meaning of sacramentum.