Why was the novel 'Of Mice and Men' given that title?

The novel 'Of Mice and Men' was written by John Steinbeck in 1937. Throughout the plot various things go wrong for different people. If it had been a Shakespearean play it might have been called a tragedy.

The underlying 'realities of life' in this story were underscored by Robert Burns' poignant poem "To A Mouse, on Turning Her Up in Her Nest, With the Plough" (1795). It contains the famous lines, "The best laid schemes o' mice an' men / Gang aft agley" (translated as "The best laid plans of mice and men / go oft awry").