costermonger n.

"large variety of apple," late 14c., coster; late 13c. in Anglo-Latin, perhaps from Anglo-French or Old French coste "rib" (from Latin costa "a rib;" see coast (n.)), if the notion is "a large apple with prominent 'ribs,' " i.e. one having a shape more like a green pepper than a plain, round apple. Also applied derisively to "the head" on resemblance to an apple. The word was common 14c.-17c. but later was limited to fruit-growers.

Old English mangere "merchant, trader, broker," agent noun from mangian "to traffic, trade," from Proto-Germanic *mangojan (source also of Old Saxon mangon, Old Norse mangari "monger, higgler"), from Latin mango (genitive mangonis) "dealer, trader, slave-dealer," which is related to mangonium "displaying of wares."

Not in Watkins or de Vaan, but Buck (with Tucker) describes it as "one who adorns his wares to give them an appearance of greater value" and writes it is probably a loan-word based on Greek manganon "means of charming or bewitching."

Used in combinations in English at least since 12c. (fishmonger, cheesemonger, etc.); since 16c. chiefly with overtones of petty and disreputable (for example ballad-monger "inferior poet," 1590s; scandal-monger).

It is a curious instance of the degradation through which words go, that what was in the Saxon period the designation for the most elevated description of merchant, mangere, is now only a term for small dealers, and principally in petty wares, monger. [Thomas Wright, "Anglo-Saxon and Old English Vocabularies," 1884]