"arithmetic, music, geometry, astronomy," 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 late 15c. in English with the sense "having four roads."
