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.

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

The boundaries of the municipality are identical to those of the district of the same name in Portuguese Timor.

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