The description of the word you requested from the astronomical dictionary is given below.
Helios = [Greek] Sun; kentrum = [Greek] center, middle
Heliocentric means it has the Sun as its center.
Heliocentric coordinate systems have the center of the Sun for their origin, and are almost always rectangular coordinate systems, but vary in the directions of the coordinate axes. Oft-used heliocentric coordinate systems are the equatorial heliocentric coordinate system and the ecliptic heliocentric coordinate system.