How did 'Of Mice and Men' get its name?

Answer 1

It's from the poem To a Mouse by Robert Burns:

But, Mousie, thou art no thy lane
In proving foresight may be vain:
The best laid schemes o' mice an' men
Gang aft a-gley,
An' lea'e us nought but grief an' pain,
For promised joy.

Answer 2

John Steinbeck got the title "Of Mice and Men" from a poem by Robert Burns, "To a Mouse," which contains the line "The best laid schemes o' mice an' men gang aft agley." Steinbeck uses this title to convey the theme of the novel, that even the best intentions can go awry in the face of larger forces beyond one's control.