Quasar was coined in the 1960s, and is a combination of the words quasi and stellar; when first discovered these objects were seen to be powerful sources of radio waves but look like stars, so they were called quasi-stellar radio sources.

However, most of the accretion onto SMBHs is expected to be heavily obscured by dust and gas, making the identification of the most obscured AGN population very challenging, even in the deepest X-ray surveys.