what are keksies -- or what were they in Shakespeare's day?

I believe 'keksies' are also known as 'keck' or 'kicksies' - you can google both and see pictures. (It is another name for cow parsley or wild chervil. See fuller definition below:

Anthriscus sylvestris, known as cow parsley, wild chervil, wild beaked parsley, keck, or Queen Anne's lace, is a herbaceous biennial or short-lived perennial plant in the family Apiaceae, genus Anthriscus. It is also sometimes called mother-die (especially in the UK), a name that is also applied to the common hawthorn. It is native to Europe, western Asia and northwestern Africa; in the south of its range in the Mediterranean region, it is limited to higher altitudes. It is related to other diverse members of Apiaceae, such as parsley, carrot, hemlock and hogweed.