Derived probably from the Hebrew jobel, ram's horn, which was used to proclaim certain times of rejoicing, confused with the Latin jubilo, to shout; a time of joy, and of pardon; "Thou shalt sanctify the fiftieth year, and proclaim remission to all the inhabitants of thy land: for it is the year of jubilee" (Leviticus 25).
Every fiftieth year absent members of a household met together, Hebrew slaves were freed, debts remitted, and land returned to its former owners.
Every seventh year was also observed.
This is the spirit of jubilees in the Church, the first of which is traced to 1300, marked by pilgrimages to Rome, special services there and throughout Christendom.
These jubilees have been repeated, when possible, at regular intervals and on occasions of extraordinary rejoicing, as during the year 1929, the fiftieth anniversary of the priesthood of Pius XI.
The chief ceremony is the opening at the beginning, and the closing at the end; of the "holy doors" in each of the basilicas the pilgrims visit in Rome, two of them being Saint Peter's and Saint John Lateran.
This ceremony symbolizes the right of sanctuary, which goes back to pagan times and which was actually then observed on the site of the Lateran.
New Catholic Dictionary