late Old English bite, "a biting, an act of piercing with the teeth;" c. 1200, "a mouthful, a morsel of food," from Proto-Germanic bitiz (source also of Old Frisian biti "a bite, a cut, penetration of a weapon," Old Norse bit "a bite," Old Saxon biti, Middle Dutch bete "a bite, bit"), from the source of bite (v.). It is attested from early 15c. as "a mark left by biting," by 1865 as "the catch or hold of one mechanical part on another."
Old English bitan "to pierce or cut with the teeth" (class I strong verb; past tense bat, past participle biten), from Proto-Germanic *beitanan (source also of Old Saxon bitan, Old Norse and Old Frisian bita "cut, pierce, penetrate," Middle Dutch biten, Dutch bijten, German beissen, Gothic beitan "to bite"), from PIE root *bheid- "to split," with derivatives in Germanic referring to biting.
To bite the bullet is said to be 1700s military slang, from old medical custom of having the patient bite a lead bullet during an operation to divert attention from pain and reduce screaming. Figurative use of this is from 1891; the custom itself attested from 1840s.
Figurative bite (one's) tongue "refrain from speaking" is by 1590s; to bite (one's) lip to repress signs of some emotion or reaction is from early 14c. To bite off more than one can chew (c. 1880) is U.S. slang, from plug tobacco.
To bite the dust "be thrown or struck down," hence "be vanquished, die, be slain, perish in battle" is from 1750, earlier bite the ground (1670s), lick the dust (late 14c.), which OED identifies as "a Hebraism," but Latin had the same image; compare Virgil's procubuit moriens et humum semel ore momordit.
Old English lufu "feeling of love; romantic sexual attraction; affection; friendliness; the love of God; Love as an abstraction or personification," from Proto-Germanic *lubo (source also of Old High German liubi "joy," German Liebe "love;" Old Norse, Old Frisian, Dutch lof; German Lob "praise;" Old Saxon liof, Old Frisian liaf, Dutch lief, Old High German liob, German lieb, Gothic liufs "dear, beloved"). The Germanic words are from PIE root *leubh- "to care, desire, love."
The weakened sense "liking, fondness" was in Old English. Meaning "a beloved person" is from early 13c. The sense "no score" (in tennis, etc.) is 1742, from the notion of playing for love (1670s), that is, for no stakes. Phrase for love or money "for anything" is attested from 1580s. The phrase no love lost (between two people) is ambiguous and was used 17c. in reference to two who love each other well (c. 1640) as well as two who have no liking for each other (1620s, the usual modern sense).
To fall in love is attested from early 15c.; to be in love with (someone) is from c. 1500. To make love is from 1570s in the sense "pay amorous attention to;" as a euphemism for "have sex," it is attested from c. 1950. Love affair "a particular experience of love" is from 1590s. Love life "one's collective amorous activities" is from 1919, originally a term in psychological jargon. Love beads is from 1968. Love bug, imaginary insect, is from 1883. Love-handles "the fat on one's sides" is by 1967.
"Even now," she thought, "almost no one remembers Esteban and Pepita but myself. Camilla alone remembers her Uncle Pio and her son; this woman, her mother. But soon we shall die and all memory of those five will have left the earth, and we ourselves shall be loved for a while and forgotten. But the love will have been enough; all those impulses of love return the love that made them. Even memory is not necessary for love. There is a land of the living and a land of the dead and the bridge is love, the only survival, the only meaning." [Thornton Wilder, "Bridge of San Luis Rey," 1927]
Old English lufian "to feel love for, cherish, show love to; delight in, approve," from Proto-Germanic *lubojanan (source also of Old High German lubon, German lieben), a verb from the root of love (n.). Weakened sense of "like" attested by c. 1200. Intransitive sense "be in love, have a passionate attachment" is from mid-13c. To love (someone) up "make out with" is from 1921. To love and leave is from 1885.
This truth came borne with bier and pall,
I felt it, when I sorrow'd most,
'Tis better to have loved and lost,
Than never to have loved at all —
[Tennyson, "In Memoriam"]