An increasingly common, sociologically ominous phenomenon of late 20th century America is the habit people have of introducing themselves by their first names only. "Hi, I'm Steve."

"Hi, I'm Fran."

Steve who? Fran what? Where's the rest of Steve and Fran?

The phenomenon is pervasive. It occurs at both formal social encounters and chance meetings. Truck drivers do it ("Hi, I'm Bud"). Teenagers do it ("Hi, I'm Mumbles"). Blacks do it ("Hi, I'm Tyrone"). WASPs do it ("Hi, I'm Nigel"). Disco partners do it ("Hi, I'm Natasha). It happens from Boston to Bakersfield.

It's a bit like meeting a stranger and asking him where he's from, and he says, "America." Or better: "Hi, I'm Tony. I'm from the landscape."

First names are skeletal. An unadorned Steve or Fran or Tony needs a McTavish or an Oppenheimer or a Mzyrskyviski to lend a little bulk, a little gravity, something on which to anchor.

Talking with someone with only a first name is like watching a person displaying only one profile in a crowded room. Why is he keeping the other turned against the wall? Is he hiding something? A wart? Dueling scars?

Using only first names has even become institutionalized, though in a gratuitous way. Waitresses' nameplates (Sue, Stella, Jo) give a truncated yet unsolicited hint of who's bringing the soup. Gas station attendants have their names (Buzz, Bill, Doogie) woven irreversibly into their uniform shirts. Long-distance telephone operators announce: "Cheryl. What city?"

All this pre-packaged informality, however, is simply a perverse variant of America's full-name phobia.

What is the root cause of this reticence with names in this otherwise unabashedly open generation? Is it an unconscious search for anonymity, an avoidance of commitment or permanence in this live-for-the-moment narcissistic age? Or is it perhaps a social outcropping of the already well-established tendency of Americans to speak in reduced approximations of the original English language ("Like wow, man, outtasight."), thus communicating only minimally necessary sounds without being held to any complicating specifics, i.e., being cool? (To approximate is to be cool.)

Socologists are divided on the issue. Dr. Billy (he did not give his last name), professor of general behavior east of the Mississippi, said in a recent interview that the true reason that people use only their first names is buried in the rich psychological loam betwee the id and the superego.

"Nominative matrix," he said, "finds collective cathaxis in quasi-archetypical numeratives, especially when interfaced with implosive correlatives on a prioritized basis.

Be that as it may, a case still can be made for disclosing the last name in social encounters. A surname, be it lofty or humble, tells us much about its bearer and lends him a certain unique character that the name Steve or Fran by itself somehow fails to convey. Many surnames are prototypically Irish or Polish or French or otherwise ethnically helpful. This in turn may give some suggestion as to the bearer's religion, politics, geographic origins and food preferences.

But more important, a complete name -- first, last and middle initial -- is filled with a special quality and essence of its own, a sound and imagery inherent in itself that imparts additional panache to the bearer. The dreariest clerk cowering in the corner at a Christmas party is somehow elevated when he tells you his name is Augustus J. Phalanthrope, rather than just "Gus." The smoldering-eyed vamp with the neo-blond Farrah Fawcett hairdo, on the other hand, falls into proper perspective when she acknowledges, after all, that she is not Svetlana but Doris Jean Suggins.

The sounds of names are filled with meaning. Short, percussive names like Clampf, Glubb and Batts suggest combative energy. Long, sonorous names like Vanderveldt and Feliciano bring to mind tall, willowy people with faint smiles. People named Babbington bounce, or at least ought to. People named Farthingdale daydream. People do a great disservice to humanity when they declare but a part of themselves. Without our full names, we sink irrevocably into the sea of blandness where Steve and Fran now dwell.