On September 28, 2003, Pope John Paul II publicly named thirty new cardinals.
An additional cardinal was named "in pectore", that's to say secretly (literally, "in the breast").
This practice was introduced because sometimes revealing the name would cause problems for the new cardinal
- if he lives in a country where the Church is oppressed, for instance. During the Cold War, many bishops
behind the iron curtain were promoted in pectore.
The secrecy is absolute: there are no official records, and nobody is notified, not even the new cardinal.
According to the law, if the pope dies without revealing the name, the in pectore cardinal stands no chance of
being officially promoted.
If the pontiff personally discloses the name (even if indirectly, and not publicly) then the new cardinal
joins the College of Cardinals, called "Collegio Cardinalizio".
The newcomer's rank and privileges are computed starting from the in pectore announcement,
not from disclosure of the name.
Shortly after the death of John Paul II, on April 2, 2005, there was much speculation about a statement that
he made on his deathbed to the Secretary of State or to some other cardinals about an envelope containing the
name of the in pectore.
Even in this roundabout fashion the promotion would be considered valid. The new cardinal could be one of
the Chinese bishops currently in jail, or Wojtyla's personal secretary, Stanislao Dziwisz.
It seems that the Italian form "in petto" is quite common everywhere but in Italy. Go figure. (Thanks JudyT!)