cerulean (adj.)youdaoicibaDictYouDict
1660s, with -an + Latin caeruleus "blue, dark blue, blue-green," perhaps dissimilated from caelulum, diminutive of caelum "heaven, sky," which is of uncertain origin (see celestial). The Latin word was applied by Roman authors to the sky, the Mediterranean, and occasionally to leaves or fields. As a noun, from 1756.
phycobiontyoudaoicibaDictYouDict
"The algal component of a lichen; any alga which is associated with a fungus to form a lichen (occasionally: specifically a green alga, as distinct from a blue-green alga)", 1950s. From phyco- + -biont.
phycochromeyoudaoicibaDictYouDict
"In early use: a blue-green pigment (believed to be a combination of chlorophyll and phycocyan) present in blue-green and certain other algae. Later: any photoconvertible pigment (phycocyanin, phycoerythrin, etc.) present in algae and cyanobacteria (blue-green algae)", Mid 19th cent.; earliest use found in Quarterly Journal of Microscopical Science. From phyco- + -chrome, after German Phycochrom. With sense 1 compare French phycochrome.