I asked this question on a mailing list about 5 years ago, this is one answer

I always thought a nurse-child was a young child or baby who was "nursed" (breast-fed) by a person other than its mother. Some Victorian Ladies either couldn't or wouldn't breast feed their babies and so paid another woman to do this for her. These women would have just lost their own baby and still
have milk. It was quite common in the towns. Children were said to be "at nurse" until about 5 years old. Sometimes the nurse-mother would live in with the child's family, and sometimes the child would stay for periods with the nurse-mother.

Also see
http://victoria.tc.ca/~tgodwin//dunc...nts/nurse.html

For full Q & A's see my question at http://archiver.rootsweb.com/th/read...-08/1029221822 and the replying threads below that.