A historic example from the Mediterranean:

This is a British hydrographic chart showing
part of a Greek island. The surveying vessel, under command of
Captain Corry, sent a party of sailors to the island to
survey it. They did not like it, as can be seen from the names
of the Hills on their map:
Yam,
Yrroc, Eb
and Denmad.
If you reverse these names, it says:
May
Corry be damned!