extraordinary jubilee

late 14c., in the Old Testament sense, from Old French jubileu "jubille; anniversary; rejoicing," from Late Latin jubilaeus "the jubilee year," originally an adjective, "of the jubilee," altered (by association with Latin jubilare "to shout with joy") from Greek iabelaios, from iobelos, from Hebrew yobhel "jubilee," formerly "a trumpet, ram's horn," literally "ram."

The original notion was of a year of emancipation of slaves and restoration of lands, to be celebrated every 50th year (Levit. xxv:9); it was proclaimed by the sounding of a ram's horn on the Day of Atonement. The Catholic Church sense of "a period for remission of sin penalties in exchange for pilgrimages, alms, etc." was begun in 1300 by Boniface VIII. The general sense of "season of rejoicing" is first recorded mid-15c., though through early 20c. the word kept its specific association with 50th anniversaries. As a type of African-American folk song, it is attested from 1872.