An upright man signifies the chief or principal of a crew. The vilest, stoutest rogue in the pack is generally chosen to this post, and has the sole right to the first night’s lodging with the dells, who afterwards are used in common among the whole fraternity. He carries a short truncheon in his hand, which he calls his filchman, and has a larger share than ordinary in whatsoever is gotten in the society. He often travels in company with thirty or forty males and females, abram men, and others, over whom he presides arbitrarily. Sometimes the women and children who are unable to travel, or fatigued, are by turns carried in panniers by an ass, or two, or by some poor jades procured for that purpose.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Upright * UpstartsNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes