One of the important parts of the Berit Mila ceremony is the Keri’at Shem – naming the baby.
Hacham Yaakob Hillel, in his edition of Machshireh Mila (a work on the laws of Mila by Hacham Eliyahu Shama, Chief Rabbi of Aleppo, d. 1814), appended a section entitled "Ateret Shalom" addressing several aspects of Berit Mila. In this appendix (p. 22), he cites the comments of the Arizal (Rav Yishak Luria of Safed, 1534-1572) in Sha’ar Ha’gilgulim (listen to audio recording for precise citation) regarding the significance of the name that parents choose for their child. The Arizal writes that the name given to a child by his or her parents is not at all coincidental, as G-d Himself has them choose the name suited for the child’s soul. The verse in Tehillim (46:9) says of G-d, "Asher Sam Shamot Ba’aretz," which can be read as, "Asher Sam Shemot Ba’aretz" – "who places names on earth," referring to His ensuring that parents choose the appropriate name for their child. The Zohar explains on this basis the verse, "Eleh Toledot Noah, Noah Ish Sadik" ("These are happenings of Noah, Noah was a righteous man" – Bereshit 6:9). The phrase "Eleh Toledot Noah Noah" implies that Noah had this name twice – once in the heavens, at the root of his soul, and once here in this world. At the time a child is named, G-d inspires the parents and endows them with special intuition to choose the name that is uniquely appropriate for their newborn child’s soul.
Hacham Yaakob proceeds to cite the work Hesed Le’Abraham (by Rav Abraham Azulai, 1570-1643) as stating that a child must not be named before his Berit, since as long as the Orla (foreskin) has yet to be removed, the child is in a state of impurity that does not allow his soul to enter. The soul can arrive only after the Berit, and thus only at that point can the child receive his name, which reflects the spiritual origins and essence of his Jewish soul. Hacham Yaakob also cites the work Kiseh Eliyahu Ha’nabi (a work devoted to various aspects of the prophet Eliyahu) as explaining on this basis the expression, "Ve’yikareh Shemo Be’Yisrael" ("And his name shall be called in Israel") with which a baby is customarily named. Once the baby has been circumcised, he now becomes a "Yisrael," as he receives his Jewish soul at that point, and so at that moment he becomes eligible to receive "Shemo Be’Yisrael" – his Jewish name, which corresponds to the essence of his soul.
This Kabbalistic understanding of a child’s naming assumes great practical significance in the case of a child who, due to a medical condition, Heaven forbid, cannot be circumcised on his eighth day. In such a case, such as if the child was born prematurely, is jaundiced, or suffers from some illness which requires delaying the circumcision, the family might wish to give him a name that can be used in the prayers recited on his behalf. Is this allowed, or should the child not be given a name until after the circumcision, even if the circumcision is delayed due to illness?
This question was addressed in the work Az Nidberu (13:73), where the author innovatively suggests that in the case of a premature birth, the child is not actually considered to have an "Orla," because he is not really considered a full-fledged child at this point. As such, he can be given a name despite having yet to be circumcised. The Az Nidberu tells of a number of Sadikim who indeed named children before the Berit. In light of what we have seen, however, it would seem that according to Kabbalistic tradition, this would not be appropriate, as the child’s soul – to which his name corresponds – does not arrive until the Berit. Hacham Yishak Yosef, in Yalkut Yosef, cites both opinions, noting that according to Kabbalistic teaching, it is improper to name a child before his Berit even if the circumcision is delayed due to illness. When people pray for the child in such a case, they refer to him simply as "Tinok (‘infant’) the son of so-and-so," instead of a name. This appears to be the accepted practice.
In conclusion, it is worth emphasizing that the moment of a child’s naming is exceedingly significant, as the parents experience a certain degree of Ru’ah Ha’kodesh (prophetic insight) in choosing the appropriate name. Of course, parents must think very carefully before choosing a name, and assure that the name they select is proper. Moreover, given the quasi prophetic stature of a child’s naming, a person’s name should not be changed without consultation with a proficient Rabbi. Changing a person’s name is not simply a matter of making a declaration at the time of the Torah reading. It is akin to "surgery" on the soul, as the name is associated with a person’s soul. Therefore, a name should be changed only after consultation with a Rabbi who has expertise in this area of Jewish tradition.
Summary: According to Kabbalistic teaching, a baby should not be named before his Berit Mila. Therefore, if a baby is ill, Heaven forbid, thus necessitating the delaying of the Berit, he should not be named. People praying for the child should refer to him simply as "Tinok," instead of a name. The name given by parents for their child is very significant, and thus a person’s name should not be changed without first consulting with a competent Rabbinic scholar.