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Old English besprecan "speak about, speak against, complain," from be- + sprecan "to speak" (see speak). A common Germanic compound (cf. Old Saxon bisprecan, Dutch bespreken, Old High German bisprehhan, German besprechen); originally "to call out," it evolved a wide range of meaning in English, including "speak up," "oppose," "request," "discuss, "arrange," and "to order (goods)" (1580s).
The connection of the senses is very loose; some of them appear to have arisen quite independently of each other from different applications of BE- pref. [OED]