Such symbolic names are often intended, by the author, to illuminate the character's significance or place in the plot.
The names used in Stranger do not seem to me to directly alter or illuminate the plot as such. One could replace them with random names out of a telephone book without changing the plot. When they have significance, it seems to be in underlining the character, the nature, of each of these fictional personas. One cannot, of course, be sure just what significance Heinlein himself attached to each name.
As seen here and here the name "Michael" comes from a Hebrew phrase אֵמִיכָאֵל (Mikha'el) meaning "Who is like God", and in traditional Christian accounts the Archangel Michael is the leader of the angels loyal to God against those who revolted, and in the Book of Daniel is described as the protector of Israel. He is sometimes depicted as God's deputy or chief assistant.
Valentine Michael Smith (VMS) in Stranger is able to work literal miracles. He shows people how to act properly, how to live the good life, and within the "theology" of the book is, for a time at least, the only self-aware divine being on Earth. The symbolism of the name reinforces this, and shoes the author's affirmation of VMS's good intentions and spiritual power.
"Smith is an occupational name meaning creator or fabricator. VMS does create the Church of All Worlds. But probably more significant, "Smith" has become the classic autonomous name, the stereotypical alias. It has become a modern analogue of "Everyman". VMS starts as a ransom generic person, "the man from mars" and gradually becomes a more specific personality.
The Behind the Name page says:
From an English surname meaning "metal worker, blacksmith", derived from Old English smitan "to smite, to hit". It is the most common surname in most of the English-speaking world.
Moreover, an apparently offhand remark in a talk by RAH: "Who ever heard of a Martian named Smith?" seems to have been one of the initiating factors in the creation of Stranger
The Babyname page gives the meaning as:
of Latin origin meaning "ram's horn".
It also has a jubilant feel through its sound and meaning, and has had some southern popularity via Confederate general Jubal Anderson Early.
the Behind the Name page derives it from the ancient Hebrew יוּבָל, which it says means "stream" and lists as "related": Ioubal(Biblical Greek) Yuval(Biblical Hebrew) Yuval(Hebrew) with no mention of Latin. The page also notes that:
This name is mentioned in Genesis in the Old Testament as belonging to the first person to be a musician.
This page lists "ram" as an alternate meaning of the original Hebrew, and says:
He was the father of all who play the harp and flute. Jubal in Hebrew means "stream" however it could be a contraction of Jubilee, which is derived from the ram's horn - blown to signify victory or celebration.
The Wikipedia article on the biblical Jubal says:
Jubal is described as the "ancestor of all who played the harp and flute."
Jubal Harshaw in Stranger is a creative person (an author specifically) but not a musician, nor does he seem to have had any particular affinity or liking for music. In the note at the start of the uncut edition of Stranger Virginia Heinlein says that this name means "Father of All". I find no source giving that meaning or anything related to it (beyond "the father of all who play the harp and flute" which is not really the same), but such a meaning would be fitting, as the character Jubal Harshaw serves as a mentor and father figure for Mike, and to a number of other characters as well, He is seen initially as a dominant figure in his household, having something of a paternal relation ship to Anne, Dorcus, Miriam, Duke and Larry, and assumes a similar role in regard to Jill. Toward the end of the book he is addressed as "Father Jubal" by a number of Mike's followers.
The Wikipedia article on the character says:
The character's name was chosen by Heinlein to have unusual overtones, like Jonathan Hoag. The character shares a surname with radio host Ruth Harshaw, a Denver radio host on whose program Heinlein frequently appeared, likely in hommage.
It cites the first statement to an interview with RAH, and the second to the Patterson biography (vol 2 p 70).
The Behind the Name page says thst this is a:
Medieval English feminine form of JULIAN. This spelling has been in use since the 13th century, though it was not declared a distinct name from Julian until the 17th century
The same site says of Julian: "From the Roman name Iulianus, which was derived from JULIUS."
the Nameberry PAGE however, describes the name "Gillian" as "of English origin meaning 'youthful'." This page goes on to say:
In medieval England, the name Gillian was so common that it was used as a generic name for a girl, just as Jack was for a boy, hence the nursery rhyme Jack and J(G)ill and the expression "every Jack has his Jill."
A page by Family Education describes it as "Latin : Graceful, blessing; variation of Juliana"
The page from BabyNames.com says:
The name Gillian means Youthful, Downy and is of English origin ... Originally a feminine form of Julian.
The page from the Names Dictionary( says:
English: variant of Julian. Irish (Tyrone and Derry): reduced Anglicized form of Gaelic Mac Gileáin ‘son of Gileán’, a variant of the personal name Gealán, from a diminutive of geal ‘bright’, ‘white’. (apparently copied from ancestry.com)
Several sites also give a meaning of "daughter of Jupiter" or "daughter of the Gods".
Gillian Boardman often called Jill in Stranger is perhaps the single most prominent female character in the book. She is Mike's companion on his travels after leaving Jubal's home, and before founding his Church. She eventually becomes one of the two High Priestesses of the Church of All Worlds. The meaning of "girl" or "everywoman" would complement Mike's role as an "everyman". At the start of the book Jill is shown as naive, and in some ways young, although fully mature and an experienced nurse. This could seem to fit the "youthful" meaning.
The Wikipedia article on the name says:
Anne, alternatively spelled Ann, is a form of the Latin female given name Anna. This in turn is a representation of the Hebrew Hannah, which means 'favour' or 'grace.'
The page also mentions St Anne, Mother of the Virgin Mary
The BabyNames.com page gives the same origin, but mentions "merciful" as an alternate meaning.
The page from The bump says:
Anne as a girl's name is of Hebrew origin, and the meaning of Anne is "He (God) has favored me". Anne is a variant of the Hebrew names Ann and Hannah.
The last meaning might seem to apply to the character Anne's abilities as a Fair Witness, or possibly to her child, suggested to have been fathered by Mike. But neither reference is clear cut.
Similar research can be done on the other names of significant characters in the book. Most of them are of biblical origin, ultimately derived from Hebrew, and a quick online search will show the origins of most. How each meaning specifically illuminates or modifies the reader's understanding of the character would require more analysis, and be in many ways a matter of opinion. But the root meanings are easily found and mostly not in significant dispute.