mid-15c., preferrement, "furtherance of an undertaking; advancement or promotion in status; a prior claim or right," from prefer + -ment. From 1530s as "a superior place or office," especially in the Church.
late 14c., preferren, "to put forward or advance in rank or fortune, to promote (to an office, dignity, or position); further (one's interest)," from Old French preferer (14c.) and directly from Latin praeferre "place or set before, carry in front," from prae "before" (see pre-) + ferre "to carry, to bear," from PIE root *bher- (1) "to carry," also "to bear children."
The meaning "to esteem or value (something) more than others, set before others in liking or esteem" also is recorded from late 14c. and is now the usual sense. The other sense in English is preserved in preferment.
common suffix of Latin origin forming nouns, originally from French and representing Latin -mentum, which was added to verb stems to make nouns indicating the result or product of the action of the verb or the means or instrument of the action. In Vulgar Latin and Old French it came to be used as a formative in nouns of action. French inserts an -e- between the verbal root and the suffix (as in commenc-e-ment from commenc-er; with verbs in ir, -i- is inserted instead (as in sent-i-ment from sentir).
Used with English verb stems from 16c. (for example amazement, betterment, merriment, the last of which also illustrates the habit of turning -y to -i- before this suffix).
The stems to which -ment is normally appended are those of verbs; freaks like oddment & funniment should not be made a precedent of; they are themselves due to misconception of merriment, which is not from the adjective, but from an obsolete verb merry to rejoice. [Fowler]
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Harper, D. (n.d.). Etymology of preferment. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/preferment