Fair exchange is no robbery

What's the meaning of the phrase 'Fair exchange is no robbery'?

An exchange of two things of equal value is a reasonable and honest trade.

What's the origin of the phrase 'Fair exchange is no robbery'?

The proverbial saying 'fair exchange is no robbery' is first found in a place we might expect to find it, that is, an early and comprehensive collection of English proverbs. There are a few of such but, in this case, it is John Heywood's 1546 glossary A dialogue conteinyng the nomber in effect of all the prouerbes in the englishe tongue:

Though chaunge be no robbry for the changed case.

Apart from what it means and where it originated, there's not a great deal more to be said about this proverb.

See also: the List of Proverbs.