Green’s Dictionary of Slang

erie n.

[SE ear]

In compounds

earysipelas kid (n.) [pun on SE erysipelas, a skin infection]

(S.Afr. Und.) an eavesdropper .

erie canal (n.) [pun on SE ear + Erie Canal, a canal in New York State between the Hudson River and Lake Erie]

[1930s] an eavesdropper.

In phrases

on the erie (also on the ear-ie)

1. see on the earhole under earhole n.

2. [1920s+] (US Und./prison, also on the earie, …eary) eavesdropping; also used as a warning.