1560s, "distinguished by greatness, renowned," from Latin illustris "lighted, bright, brilliant;" figuratively "distinguished, famous," probably a back-formation from illustrare "make light, light up, illuminate," figuratively "embellish, distinguish, make famous" (see illustration). Replaced illustre in same sense (mid-15c.), from French illustre.
c. 1500, pencellen, "apply (gold or silver) in manuscript illustration;" 1530s, "to mark or sketch with a pencil-brush," from pencil (n.). In reference to lead pencils from 1760s. Related: Penciled; penciling. To pencil (something) in in the figurative sense of "arrange tentatively" (on the notion of being erasable) is attested by 1942.
mid-15c., exemplificacioun, "illustration or demonstration by example," from Anglo-French exemplificacion "attested copy or transcript of a document" (late 14c.) and directly from Medieval Latin exemplificationem (nominative exemplificatio), noun of action from past-participle stem of exemplificare "to illustrate" (see exemplify). Holinshed had a back-formation exemplificate.