(FB 1550420896 Timestamp)
c. 1300, “pack of animals,” possibly related to Middle English rablen “to gabble, speak in a rapid, confused manner,” probably imitative of hurry, noise, and confusion (compare Middle Dutch rabbelen, Low German rabbeln “to chatter”). Meaning “tumultuous crowd of vulgar, noisy people” is from late 14c.; applied contemptuously to the common or low part of any populace from 1550s.
(someone used the term and I realized I didn’t know its origin)