The term archaerhodopsin is a portmanteau of archaea (the domain in which the proteins are found) and rhodopsin (a photoreceptor responsible for vision in the mammalian eye).
:archaea from Ancient Greek [https://en.wiktionary.org/wiki/%E1%BC%80%CF%81%CF%87%CE%B1%E1%BF%96%CE%BF%CF%82#Ancient_Greek ἀρχαῖα] (arkhaîa, "ancient"), the plural and neuter form of [https://en.wiktionary.org/wiki/%E1%BC%80%CF%81%CF%87%CE%B1%E1%BF%96%CE%BF%CF%82#Ancient_Greek ἀρχαῖος] (arkhaîos, "ancient").
:rhodopsin from Ancient Greek [https://en.wiktionary.org/wiki/%E1%BF%A5%CF%8C%CE%B4%CE%BF%CE%BD#Ancient_Greek ῥόδον] (rhódon, "rose"), because of its pinkish color, and [https://en.wiktionary.org/wiki/%E1%BD%84%CF%88%CE%B9%CF%82#Ancient_Greek ὄψις] (ópsis, "sight").