tattler, n.¹ — Green’s Dictionary of Slang

tattler n.¹

[its light ‘tells tales’ on criminal activity]

(UK Und.) the moon.

1718		C. Hitchin Regulator 20: The Tattler is up, alias the Moon shines.
1719		A. Smith Lives of Most Notorious Highway-men, etc. (1926).
1768		(con. 1710–25) Tyburn Chronicle II in Groom (1999) xxix: The Tattler is up The Moon shines.
1834		(con. 1737–9) W.H. Ainsworth Rookwood (1857) 274: Oliver whiddles – the tattler old!