From The Collaborative International Dictionary of English v.0.48:
Snack \Snack\, n. [See Snatch, v. t.]
1. A share; a part or portion; -- obsolete, except in the
colloquial phrase, to go snacks, i. e., to share.
[1913 Webster]
At last he whispers, "Do, and we go snacks." --Pope.
[1913 Webster]
2. A slight, hasty repast. [Colloq.]
[1913 Webster]