Literal meaning.

This phrase, which is always used with a sense of regret, was coined by Robert Burns and used in his poem From Man was made to Mourn: A Dirge, 1785:

'Many and sharp the num'rous ills
Inwoven with our frame!
More pointed still we make ourselves
Regret, remorse, and shame!
And Man, whose heav'n-erected face
The smiles of love adorn, -
Man's inhumanity to man
Makes countless thousands mourn!