According to Jewish tradition, a person’s name is the spiritual conduit through which they receive G‑d’s bounty.

Accordingly, in the case of grave illness or other extreme misfortune, the choice may be made (in consultation with an expert rabbi) to either change a name or add to an existing one. The basis for this practice comes from G‑d Himself, who modified Abraham’s and Sarah's names, opening up the conduits to fertility for them.1

When we add a name for someone who is gravely ill, we often choose life-affirming names like Chaya (for females) or Chaim (for males), which mean “life” in Hebrew, or Alta (for females) and Alter (for males), which mean “old” in Yiddish, a milestone we wish for this person to reach. Another common choice for males is Rafael (“G‑d heals”).

The new name is typically added before the existing name, so, for example, Yosef becomes Chaim Yosef and not Yosef Chaim.

Procedures for adding a name can vary. Some arrange for a relative to be called to the Torah, and for a ‘Mi sheBerach’ prayer for healing to be said using the new name.

And many follow the procedure outlined in the addenda to Tehillim Ohel Yosef Yitzchak on pages 183-185:

A group (ideally a minyan) assembles and recites Psalms: 20, 6, 9, 13, 16, 17, 18, 22, 23, 28,2 30, 31, 32, 33, 37, 38, 39, 41, 49, 55, 56, 69, 86, 88, 89, 90, 91, 102, 103, 104, 107, 116, 118, 142, 143, 148/128.

They then turn to Psalm 119, which contains 8 verses for every letter of the Hebrew alphabet; verses 1-8 begin with the letter aleph, 9-16 start with bet, etc. They thus recite the verses that spell the existing name of the patient, and then add the verses that begin with kuf, resh, ayin, shin, tet, nun, which spell kera Satan (“tear Satan”).

This is followed by the prayer for healing as well as the prayer for adding a name, which is on the bottom of page 184.

This prayer sums up the rationale behind the name change succinctly:

“... Our holy rabbis have said that three things can rescind a person’s verdict—one of which is the changing of the sick person’s name … if death was decreed for one individual, this decree was not issued for another. Therefore s/he is someone else—not the one called by [former name]. And just as his/her name was changed, so too should the decree regarding him/her be changed: from severity to compassion, from death to life, from sickness to a complete recovery for [new name] ...”

Once the new name has been added, it is important to actually use that name in real life in the prayerful wish that it bring healing, recovery and divine blessings to its bearer and his or her loved ones.