Green’s Dictionary of Slang

prig n.1

also prigg
[either Lat. pregare, to pray, or SE prig = prick = sting = rob or cheat. SE prig, meaning a carping know-all, may have similar roots, but may be based on the divine Richard Baxter (1615–91), who in 1684 associated it with the initial letters of proud ignorance]
(UK Und.)

1. [16C–19C] a ne’er-do-well who, accompanied by his woman, wanders the country, mixing villainy and legitimate work, pursuing neither, it appears, with particular enthusiasm (sometimes known as the drunken tinker n.).

2. [mid-16C–19C] (also prigman) a thief, orig. use a mendicant villain who specializes in stealing clothes from hedgerows where they are left to dry, or poultry from the farmyard.

3. [late 17C–mid-19C] a dandy, a fop.

4. [18C–mid-19C] a cheat.

5. a pickpocket; a petty thief.

In derivatives

priggicism (n.)

[early 18C] the characteristics of thieving.

priggish (adj.)

1. [late 17C–mid-19C] (UK Und.) having the characteristics of a thief.

2. having the characteristics of a conceited young dandy.

prigster (n.)

see separate entry.

In compounds

prig-napper (n.) (also prigger-napper) [nap v.1 (3)]

[late 17C–early 19C] (UK Und.) a thief-taker, thus a policeman.

In phrases

prince prig (n.) [17C–early 19C] (UK Und.)

1. a leading thief, esp. one who acts as a receiver for the robberies of colleagues.

2. the King of the Gypsies.