An inferior isn’t completely restricted in what they may do in the presence of a superior.

The origin of this proverb is unknown. What is known is that it is found first in print in a famous early collection of English proverbs, The Proverbs And Epigrams Of John Heywood, 1562:

Some hear and see him whom he heareth nor seeth not
But fields have eyes and woods have ears, ye wot
And also on my maids he is ever tooting.
Can ye judge a man, (quoth I), by his looking?
What, a cat may look on a king, ye know!
My cat’s leering look, (quoth she), at first show,
Showeth me that my cat goeth a caterwauling;
And specially by his manner of drawing
To Madge, my fair maid.