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.