Someone who works in a nursery, caring for children usually from the age of 0-4.
nurse
Generally they can just be called nursery workers If you mean a plant nursery, then they are sometimes called gardners or master gardeners.
A person who writes nursery rhymes is generally referred to as a nursery rhyme writer or a children's poet.
In hospitals and other professional situations physicians are usually addressed as, or referred to as, "Doctor."
Tech Person
a slave
Employee
someone who works for a business
hydrologist
A mathematician
moofer
A Chronogist