Vocabulary: The term “head” here refers to the person. I am not sure why “head” is used here, unless English lacks a better term. The usual connotation of “head” is “firstmost” or “principal.” I see this word as attempt to designate both the person and the position of the Messiah, with whom Benjamin’s people (and we) have entered into a relationship. That relationship places him above us. Thus, this term denotes both the Messiah as a person and his position of being our leader/ruler/master.
Culture: The significance of accepting a new name as a people is underscored by a commentary from Sir James George Frazer’s The Golden Bough which, even in abridgment, is monumental. Although Frazer’s language is somewhat condescending (e.g., “savage”), he nevertheless shows illuminates the importance attached to naming for many ancient peoples:
Unable to discriminate clearly between words and things, the savage commonly fancies that the link between a name and the person or thing denominated by it is not a mere arbitrary and ideal association, but a real and substantial bond which unites the two in such a way that magic may be wrought on a man just as easily through his name as through his hair, his nails, or any other material part of his person. In fact, primitive man regards his name as a vital portion of himself and takes care of it accordingly. Thus, for example, the North American Indian “regards his name, not as a mere label, but as a distinct part of his personality, just as much as are his eyes or his teeth, and believes that injury will result as surely from the malicious handling of his name as from a wound inflicted on any part of his physical organism. This belief was found among the various tribes from the Atlantic to the Pacific, and has occasioned a number of curious regulations in regard to the concealment and change of names.” Some Esquimaux take new names when they are old, hoping thereby to get a new lease of life. The Tolampoos of Celebes believe that if you write a man’s name down you can carry off his soul along with it. Many savages at the present day regard their names as vital parts of themselves, and therefore take great pains to conceal their real names, lest these should give to evil-disposed persons a handle by which to injure their owners.
The reality of the name-person connection was also an important part of Near Eastern culture. Bruce H. Porter of the LDS Institute of Religion in San Marcos, California, and Stephen D. Ricks of Brigham Young University note:
In the cultures of the ancient Near East, existence was thought to be dependent upon an identifying word, that word being a “name.” The name of someone (or something) was perceived not as a mere abstraction, but as a real entity, “the audible and spoken image of the person, which was taken to be his spiritual essence.” [citing W. Brede Kristensen.] According to Philo of Alexandria, the name “is like a shadow which accompanies the body.” Similarly, Origen viewed the name as the designation of the individual’s essence.
While the naming of Benjamin’s people exhibits none of Frazer’s taboos, this event obviously carried symbolic significance. (See commentary accompanying Mosiah 3:17.) Benjamin expects this new name to represent the transformation of his previously divided people into a united people. That Benjamin considers the name itself to have power is evident in how he caps the covenant with it. There is no other name by which salvation may be had (Mosiah 3:17, 5:8). Taking upon them the name of Yahweh-Messiah is not nearly so passive as a modern designation of Christian—nor even of “Latter-day Saint.” The name included all of the covenants subsumed under that name and identified the person who bore it as one of the covenant. The name of Yahweh-Messiah had the same meaning for Benjamin’s people as circumcision did for the Old World Hebrews.