no more than the man in the moon

no more than the man in the moon

1. dated Not anything of substance or real value; nothing at all. I quickly realized that Tom knew no more than the man in the moon about what had happened. I'll thank you not to lecture me on a subject about which you know no more than the man in the moon.
2. dated None (of something) or not (something) whatsoever. In this usage, a noun, adjective, or phrase is used between "no more" and "than the." How could you do something so stupid? I swear, you've no more sense than the man in the moon! It's clear they had no more interest in helping us than the man in the moon. The dangers these politicians are warning us of are no more real than the man in the moon. They're just trying to scare us into compliance.
See also: man, moon, more, no
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

man in the moon, (no more than) the

A mythical figure, hence nothing, or a figment of the imagination. Mention of the man in the moon dates from the early fourteenth century. In Troilus and Criseyde Chaucer quotes, indirectly, a myth that a man who desecrated the Sabbath was banished to the moon. By the sixteenth century, however, this turn of phrase was linked with something so distant as to be unlikely (“as farre from her thought as the man that the rude people saie is in the moone,” Edward Hall, Chronicle of Richard III, ca. 1548).
See also: man, more
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer