solar (adj.) Look up solar at Dictionary.com
mid-15c., from Latin solaris "of the sun," from sol "sun" (see sol). Meaning "living room on an upper story" is from Old English, from Latin solarium (see solarium).

Solar power is attested from 1915. Solar system is attested from c.1704. Solar plexus (1771) "complex of nerves in the pit of the stomach," apparently so called from its central position in the body. Solar cell attested from 1955. Solar panel is from 1964. Solar wind is from 1958.