Green’s Dictionary of Slang

bilk v.

[bilk n.]

1. [mid-17C+] (UK Und.) to cheat, to swindle; thus bilked adj., cheated; bilking n., cheating.

2. [19C] to evade payments, esp. of a prostitute’s client; thus bilking adj.

3. [1900s–10s] (Aus. Und.) of a prostitute, to rob a client.

In derivatives

bilker (n.)

[early 18C–1940s] one who habitually cheats, esp. in refusing to pay a bill, e.g. a cabman’s fare.

In compounds

bilking house (n.) (also bilking crib)

(US/Aus. Und.) a brothel wherein clients are robbed of their money.

In phrases

bilk the schoolmaster (v.)

[early 19C] to get knowledge without paying for it, e.g. the experience that comes with living one’s life.