mid-13c., defenden, "to shield from attack, guard against assault or injury," from Old French defendre (12c.) "defend, resist," and directly from Latin defendere "ward off, protect, guard, allege in defense," from de "from, away" (see de-) + -fendere "to strike, hit, push," attested only in compounds (such as offendere "to strike against; encounter;" infensus "aggressive, hostile"), from PIE root *gwhend- "to strike, kill" (source also of Hittite kue(n)zi "to kill," Sanskrit ghnanti "to kill; Greek theino "to slay, to kill;" Armenian jnem "to strike;" Lithuanian ginti "to protect, defend;" Old Irish gonaid "wounds, kills;" Welsh gwan "to thrust, hit;" Old Breton goanaff "to punish, sting").
It is attested from c. 1300 as "fight in defense of" (someone or something). From mid-14c. as "defend with words, speak in support of, vindicate, uphold, maintain." In Middle English it also could mean "forbid, prohibit; restrain, prevent." In the Mercian hymns, Latin defendet is glossed by Old English gescildeð. Related: Defended; defending.
c. 1300, defendour, "one who protects from injury a champion" (early 13c. as a surname), via Anglo-French from Old French defendeor, agent noun from defendre (see defend). The Latin word in this sense was defensor.
c. 1400, in the legal sense "a party sued in a court of law," from Anglo-French, Old French defendant (Modern French défendant), noun use of present participle of defendre (see defend). Earliest use in English was as a present-participle adjective meaning "defensive, defending" (c. 1300).
c. 1300, "ready and able to fight, able to defend," from Old French defensable, from Medieval Latin defensibilis, Late Latin defensibilem, from Latin defens-, past-participle stem of defendere (see defend). Meaning "capable of being defended" is from late 14c., sense of "contributing to defense" is from c. 1400; that of "that may be vindicated" is from early 15c. Related: Defensibility.
c. 1400, "serving to defend, proper for defense; of the nature of defense," from Old French defensif (14c., Modern French défensif) and directly from Medieval Latin defensivus, from defens-, past participle stem of Latin defendere (see defend). Of persons, "alert to reject criticism," from 1919. Related: Defensively; defensiveness.
As a noun, "that which defends or serves for defense," c. 1400, originally of medicines. Meaning "posture or attitude of defense" is from c. 1600.
early 14c., offenden, "to disobey or sin against (a person, human or divine)," a sense now obsolete, from Old French ofendre "hit, attack, injure; sin against; antagonize, excite to anger" and directly from Latin offendere "to hit, thrust, or strike against," figuratively "to stumble, commit a fault, displease, trespass against, provoke," from assimilated form of ob "in front of against" (see ob-) + -fendere "to strike" (found only in compounds; see defend).
Meaning "to violate (a law), to make a moral false step, to commit a crime" is from late 14c. Meaning "to wound the feelings of, displease, give displeasure to, excite personal annoyance or resentment in" is from late 14c. The literal sense of "to attack, assail" (late 14c.) is obsolete, but it is somewhat preserved in offense and offensive. Related: Offended; offending; offendedness.
c. 1300, "action of guarding or shielding from attack or injury; act of defending by fighting; a fortified place of refuge," from Old French defense, from Latin defensus, past participle of defendere "ward off, protect" (see defend). It also arrived (without the final -e) from Old French defens, from Latin defensum "thing protected or forbidden," neuter past participle of defendere.
Middle English defens was assimilated into defense, but not before it inspired the alternative spelling defence, via the same tendency that produced hence (hennis), pence (penies), dunce (Duns). Webster made the -se form standard in U.S., but British has preferred defence, and compare fence (n.).
Meaning "a speech or writing intended to repel or disprove a charge or accusation" is from late 14c., as is the sense of "method adopted by one against whom a lawsuit has been brought." Meaning "science of defense against attack" (in fencing, boxing, etc.) is from c. 1600. Used by 1935 as a euphemism for "national military resources," but the notion (non-euphemistic) was in Middle English: man of defense "warrior," ship of defense "warship." Defenses "natural weapons of an animal" is by 1889. Defense mechanism in psychology is from 1913.
c. 1300, garite, "turret, small tower on the roof of a house or castle," from Old French garite "watchtower, place of refuge, shelter, lookout," from garir "defend, preserve," which is from a Germanic source (compare Old English warian "to hold, defend," Gothic warjan "forbid," Old High German warjan "to defend"), from Proto-Germanic *warjan, from PIE root *wer- (4) "to cover." Meaning "room on uppermost floor of a house," especially a room with a sloping roof, is from early 14c. See attic. As the typical wretched abode of a poor poet, by mid-18c.