We recall here that Helam is the name of the first man baptized by Alma in the waters of Mormon (Mosiah 18:12-13). That the land should be named Helam suggests that Helam was a man of some importance in Lehi-Nephi, and brought with him that status to the people of Alma, despite the leveling of economic rank that occurred with Alma's people. This further suggests that much of his prominence was based on personal qualities that would continue to be apparent even after social trappings of the culture of Lehi-Nephi were stripped away.
It is probable that the same reasons that led Alma to choose Helam as the first were those that led the land to be named after him. While we might expect that the land might be named for Alma, it was not. This may be related to Alma's abhorrence of even the suggestion of kingship. Since it was typical to name the land for the political leader (land of Nephi, land of Zarahmela, land of Mormon are explicit examples) Alma may have declined to have the land named for him lest there be attached assumptions of his "kingship" even if undeclared.
Textual: The printer's manuscript has Helaman here which was corrected prior to the first printed edition to Helam. See the analysis which follows Mosiah 18:12 for details.