"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."

late 14c., from French quadrupler, from Late Latin quadruplare "make fourfold, multiply by four," from Latin quadruplus (adj.) "quadruple, fourfold," from quadri- "four" (from PIE root *kwetwer- "four") + -plus "-fold" (see -plus).

1550s, from French quadruple (13c.), from Latin quadruplus "fourfold," from quadri- "four" (from PIE root *kwetwer- "four") + -plus "-fold" (see -plus).

1570s, from Latin quadruplicationem (nominative quadruplicatio), noun of action from past-participle stem of quadruplicare (see quadruplicate (v.)).