IPA: /ˈɛkstɜrn/
KK: /ˈɛkstɜrn/
A person who is connected to an institution but does not live there, often used to refer to a nonresident doctor or medical student.
The extern worked at the hospital during the summer to gain experience.
Extern is derived from "ex-" (meaning out of or from) and "ternus" (meaning lasting or eternal). The word refers to something that is from outside or external to a particular context.
Think of something that comes 'from outside' ('ex-') — that's why 'extern' refers to something external.