heir n.

1530s, "inheritance, succession," from French hérédité, from Old French eredite "inheritance, legacy" (12c.), from Latin hereditatem (nominative hereditas) "heirship, inheritance, an inheritance, condition of being an heir," from heres (genitive heredis) "heir, heiress" (from PIE root *ghe- "to be empty, left behind," source also of Greek khēra "widow"). Legal sense of "inheritable quality or character" first recorded 1784; the modern biological sense "transmission of qualities from parents to offspring" seems to be found first in 1863, introduced by Herbert Spencer.

late 14c., "indisputable, clearly understood;" c. 1400, "easily seen or perceived," from Old French aparant "evident, obvious, visible," from Latin apparentem (nominative apparens) "visible, manifest," present participle of apparere "appear, come in sight" (see appear).

First attested in phrases such as heir apparent (see heir). The meaning "superficial, spurious" is from c. 1400; that of "appearing to the senses or mind but not necessarily real" is from 1640s. Apparent magnitude in astronomy (how bright a heavenly body looks from earth, as opposed to absolute magnitude, which is how bright it really is) is attested from 1875. Middle English had noun forms apparence, apparency, but both are obsolete since 17c.