This phrase is an intensifier, that is, it heightens the action indicated by the verb that follows it. For example, Don't go and eat all the leftover chicken is stronger than “Don't eat all the leftover chicken.” Similarly, Thomas Gray put it in a letter (1760): “But now she has gone ... and married that Monsieur de Wolmar.” Sometimes the and is omitted, as in Go tell Dad dinner is ready, or Go fly a kite, colloquial imperatives telling someone to do something. [c. 1300]