teaching license; teacher's license
Official certification required to teach in Japanese schools. Often used in contexts of obtaining, renewing, or holding the license.
He is studying at university to obtain a teaching license.
I needed to renew my teaching license.
教員 refers to a teacher or teaching staff, while 教員免許 is the license itself.
免許 is a general license or permit (e.g., driver's license), whereas 教員免許 specifically means a teaching license.
Compound of 教員 (teacher) and 免許 (license). The exact historical derivation is straightforward; the term has been used since the modern Japanese education system was established.