In the more than 20 years that complaints about the language in The Sun have been forwarded to my desk, never once has anyone complained about "arabbers." It has been clearly established over a long period that the city's arbabbers are African-Americans vending produce from horse-drawn carts.
The word most likely derives from the 19th-century British street arab or city arab, terms the Oxford English Dictionary defines as homeless children or adults who wandered the streets, sometimes stealing but often selling small objects. The boys of Sherlock Holmes' Baker Street Irregulars are drawn from that population.
The association of peddlers roaming the streets with the nomadic Bedouins is likely the link by which Baltimore coined its distinctive term.
When the word was adapted in Baltimore for peddlers of produce, it took a variety of forms, a-rab, a-rabber, and arabber, pronounced "AY-rab" or "AY-rabber," rather that "AIR-ab" or "AIR-abber."
Arabber is the preferred spelling of the Arabber Preservation Society, created in 1994 for the support of arabbing, "an African-American folk tradition," and that is the preferred term in The Sun's house style.
Long use, of course, does not necessarily make a derogatory term acceptable, and A-rab (yes, pronounced "AY-rab) has a history in the United States as a term for an Arab, often derogatory. There is, for example, line in Huckleberry Finn: "A whole parcel of Spanish merchants and rich A-rabs was going to camp in Cave Hollow with two hundred elephants, and six hundred camels."
That is one reason that our house style adopted the arabber spelling, to differentiate the word for Baltimore's street peddlers, working hard for a living under often-challenging circumstances, from the taint of an ethnic slur, and to celebrate a long-standing and affectionate local tradition.