*mare
mare (mâr) n. 1. 1. A female horse. [OE mære, mere, mȳre < PGmc. marhijō < PIE markos, horse.] 2. A malicious spirit or phantom believed to cause nightmares; an incubus. [OE mære, nightmare, monster < PGmc. marǭ, nightmare, incubus.] See also nightmare. 3. (Astronomy) A large, dark, relatively smooth plain on the moon or other celestial body, mistakenly identified as a sea by early astronomers. [L. mare, sea; also used generally to refer to a large body of salt water, a sea or ocean.] Pl. maria (mâr'ē-ə). Usage Note: While homophonous, the "mare" meaning "female horse" and "mare" meaning "nightmare" are etymologically unrelated. The astronomical "mare" is from a separate Latin root, which also denotes a general sea or ocean.
*liber
liber (lĭbər) n. 1. 1. (adj.) Free; unrestricted; having liberty. [From Latin liber, free; from Proto-Italic louðero-, from Proto-Indo-European leudh- "to grow, to spring forth."] Related to libertas (liberty) and liberalis (liberal). 2. (n.) Book; specifically, the inner bark of a tree used for writing, and by extension, a written work. [From Latin liber, inner bark of a tree, book.] Related to librarium (library) and libellus (little book). Usage Note: While homographic, these two meanings of liber are etymologically distinct, representing separate evolutions of the word within Latin. The first refers to freedom, while the second refers to the material and form of early books.