"haggle, bargain in a petty way," 1802 (implied in dickering), American English, perhaps from dicker (n.) "a unit or package of tens," especially hides (attested from late 13c.), a Germanic word (compare Swedish decker, Danish deger, German decher), which is perhaps from Latin decuria "parcel of ten" (supposedly a unit of barter on the Roman frontier; compare German Decher "set of ten things"), from decem "ten" (from PIE root *dekm- "ten") on model of centuria from centum.
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Harper, D. (n.d.). Etymology of dickering. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/dickering