Vaguely. But I always thought that was recently pregnant women producing extra milk for other people's babies.
A woman can only act as a wet-nurse if she is lactating.
It was once believed that a wet-nurse must have recently undergone childbirth. This is not necessarily true, as regular breast suckling can elicit lactation via a neural reflex of prolactin production and secretion.[3]
Some adoptive mothers have been able to establish lactation using a breast pump so that they could feed an adopted infant.