1560s, "to bulge out;" 1610s, "to strike heavily, cause to come into violent contact," perhaps from Scandinavian, probably echoic, if the original sense was "hitting" then of "swelling from being hit." It also has a long association with the obsolete verb bum "make a booming noise." To bump into "meet by chance" is from 1886; to bump off "kill" is by 1908 in underworld slang. Related: Bumped; bumping. Bumpsy (adj.) was old slang for "drunk" (1610s).
by 1751, from Medieval Latin trivium (9c.) "grammar, rhetoric, and logic," the first three of the seven liberal arts, considered initiatory and foundational to the other four (arithmetic, geometry, astronomy, and music). From Latin trivium, in classical Latin "place where three roads meet; a frequented place; public street, highway," from tri- "three" (see three) + via "road" (see via). Compare trivia and also see quadrivium.
mid-15c. (implied in congregated), "accumulate," originally of fluids in the body, from Latin congregatus, past participle of congregare "to herd together, collect in a flock, swarm; assemble," from assimilated form of com "together" (see con-) + gregare "to collect into a flock, gather," from grex (genitive gregis) "a flock" (from PIE root *ger- "to gather").
Of persons, "collect or bring together in an assembly," 1510s; intransitive sense "come together, assemble or meet in large numbers," 1530s. Related: Congregating.
"arithmetic, music, geometry, astronomy" (the four branches of mathematics, according to the Pythagoreans), by 1751, from Latin quadrivium, which meant "place where four roads meet, crossroads," from quadri- "four" (from PIE root *kwetwer- "four") + via "way, road, channel, course" (see via). Compare liberal arts, and also see trivium.
The adjective quadrivial is attested from mid-15c. in English with the sense of "belonging to the quadrivium," late 15c. with the sense of "having four roads, having four ways meeting in a point."
"curved like a circle or sphere when viewed from outside," 1570s, from French convexe, from Latin convexus "vaulted, arched," past participle of convehere "to bring together," from assimilated form of com "with, together," or "thoroughly" (see com-) + vehere "to bring, carry, convey" (from PIE root *wegh- "to go, move, transport in a vehicle").
Possibly the notion is of vaults "carried together" to meet at the point of a roof. Related: Convexity. Convex lens is from 1822.
c. 1300, defien, "to renounce one's allegiance;" mid-14c., "to challenge to fight, dare to meet in combat;" from Old French defier, desfier "to challenge, defy, provoke; renounce (a belief), repudiate (a vow, etc.)," from Vulgar Latin *disfidare "renounce one's faith" (in Medieval Latin diffidare), from Latin dis- "away" (see dis-) + fidus "faithful" (from PIE root *bheidh- "to trust, confide, persuade"). By 1670s as "dare (someone) to do something (that the challenger believes cannot or will not be done)."