The word Ermera means 'red water' in the local Mambai language.

[2] It is said that the ancestors of today's inhabitants of the municipality originated from three mountains, namely Cailitlau, Lalimlau, and Hituria, and that the name Ermera refers to the red waters flowing from those mountains.

[3] Ermera is one of only two land-locked municipalities in East Timor, the other being Aileu.

It borders Liquiçá to the north, Dili to the northeast, Alieu to the east, Ainaro to the southeast, and Bobonaro to the west.

In Marobo (Atsabe Administrative Post) are the remains of a hot springs bath from colonial times.