The word "小偷小摸" is formed by juxtaposing two similar phrases: "小偷" meaning petty thief, and "小摸" meaning petty stealing, where "小" indicates minor scale, and "偷" (steal) and "摸" (touch, here implying furtive taking) are verbs describing theft-related actions, resulting in a compound that emphasizes repeated, minor acts of theft.