Origin and history of consumption

word-forming element usually meaning "with, together," from Latin com, archaic form of classical Latin cum "together, together with, in combination," from PIE *kom- "beside, near, by, with" (compare Old English ge-, German ge-). The prefix in Latin sometimes was used as an intensive.

Before vowels and aspirates, it is reduced to co-; before -g-, it is assimilated to cog- or con-; before -l-, assimilated to col-; before -r-, assimilated to cor-; before -c-, -d-, -j-, -n-, -q-, -s-, -t-, and -v-, it is assimilated to con-, which was so frequent that it often was used as the normal form.

Proto-Indo-European root meaning "to take, distribute." 

It might form all or part of: assume; consume; emption; example; exemplar; exemplary; exemplify; exempt; exemption; impromptu; peremptory; pre-emption; premium; presume; presumption; prompt; pronto; ransom; redeem; redemption; resume; sample; Sejm; subsume; sumptuary; sumptuous; vintage.

It might also be the source of: Sanskrit yamati "holds, subdues;" Latin emere "buy," originally "take," sumere "to take, obtain, buy;" Old Church Slavonic imo "to take;" Lithuanian imu, imti "to take."

For the sense shift from "take" to "buy" in the Latin verbs, compare Old English sellan "to give," source of Modern English sell "to give in exchange for money;" Hebrew laqah "he bought," originally "he took;" and colloquial English I'll take it for "I'll buy it." 

word-forming element of Latin origin meaning "under, beneath; behind; from under; resulting from further division," from Latin preposition sub "under, below, beneath, at the foot of," also "close to, up to, towards;" of time, "within, during;" figuratively "subject to, in the power of;" also "a little, somewhat" (as in sub-horridus "somewhat rough"), from PIE *(s)up- (perhaps representing *ex-upo-), a variant form of the root *upo "under," also "up from under," which also yielded Greek hypo- and English up.

The Latin word also was used in Latin as a prefix and in various combinations. In Latin it was reduced to su- before -s- and assimilated to following -c-, -f-, -g-, -p-, and often -r- and -m-.

In Old French the prefix appears in the full Latin form only "in learned adoptions of old Latin compounds" [OED], and in popular use it was represented by sous-, sou-; as in French souvenir from Latin subvenire, souscrire (Old French souzescrire) from subscribere, etc.

The original meaning is now obscure in many words from Latin (suggest, suspect, subject, etc.). The prefix is active in Modern English; the indication generally being:

1. "under, beneath, at the bottom of;" in adverbs "down, low, lower;"

2. "inferior part, agent, division, or degree; inferior, having subordinate position" (subcontractor) also forming official titles (subaltern);

It also can indicate "division into parts or sections;" "next below, near, close to" (subantarctic); "smaller" (sub-giant); and it may be used generally as "somewhat, partial, incomplete" (subliterate).