When Jill Ammon gave birth to a baby girl in April 2004, she and her husband, Chris, were leaning pretty heavily toward naming her Isabella. Then their doctor weighed in.

Since Hurricane Isabel swept the East Coast in 2003, he told the Alexandria couple, he'd delivered "a ton" of Isabellas.

"We scratched that name pretty quickly after that and settled on Lucy," says Chris.

These days, naming a baby is serious business -- literally. It's spawned bushels of books, Web sites, even some wacky advertising opportunities. (In one of the latest examples, an Internet casino reported paying $15,000 for the right to dub a child GoldenPalaceDotCom Silverman.)

One of the process's main problems: balancing the pull of a name that seems oh-so-perfect with the fear that, in hospitals across the country, too many other parents are feeling the same affection for the same set of letters.

"In the past, there was more concern about a name sounding weird," says Laura Wattenberg, author of "The Baby Name Wizard." "Today, parents worry more that their child's name will become popular. They're more afraid of blending in than sticking out."

For the Ammons, last month's Social Security Administration release of the most popular baby names of 2004 confirmed their doctor's advice: Among girls, Isabella was ranked seventh, preceded by, in order of decreasing ubiquity, Emily, Emma, Madison, Olivia, Hannah and Abigail. Ashley, Samantha and Elizabeth finished off the Top 10. Among boys, the Top 10 were Jacob, Michael, Joshua, Matthew, Ethan, Andrew, Daniel, William, Joseph and Christopher.

In the current bestseller "Freakonomics," economist Steven D. Levitt devotes a chapter to exploring the roots of name popularity, trying to determine if there is a pattern to their rise and fall.

After studying birth certificate information for Californians born since 1961, Levitt decided there was. Names, he posits, begin their ascent by catching on with well-educated, high-income parents, then become more common (both in number and perceived quality) as they move down the socioeconomic scale.

"For every high-end baby named Stephanie or Brittany, another five lower-income girls received those names within 10 years," Levitt writes in the book.

Names that become hits among lower-end families usually then fall off popularity lists altogether. Among white Californians, for example, Lauren and Madison were among the top names with well-educated families in the 1990s. Now, they're among the most popular names for white girls overall. Meanwhile, Heather and Amber, among the top overall during the 1980s, had by the 1990s become hot picks among only lower-income families.

But what starts a name on that climb at all? Observers such as Diane Stafford, author of "50,001 Best Baby Names," thinks each year sees its own trends. Among today's inspirations, she says, are last names (like MacKenzie, Madden and Maloney), an urge for completely new, fully made-up names (Jazzline and Deshawn) and names inspired by celebrities.

These last often seem to go from obscurity to the spotlight right away. Most people, for example, had never heard of a baby being named Apple until Gwyneth Paltrow and husband Chris Martin used it last year. Sometimes, the name highlighted may have already been climbing the charts. Though Brooklyn made the papers when Victoria and David Beckham chose it for their son in 1999, it had been gaining popularity since at least 1990.

Trends and branding expert Rachel Weingarten, president of New York-based GTK Marketing Group, thinks most couples should think hard before considering a celebrity-endorsed name.

"Celebrities tend to be guilty of saddling their offspring with painful monikers in the misguided effort to make them stand out even more from the crowd," she says. "For better or worse, you're branding that child. Quirky is fine for a day or two, but Denim and Diezel? What were you thinking, Toni Braxton?"

Safer, according to Wattenberg, is the current taste for old-fashioned names such as Jacob and Olivia.

"The rule of thumb is that it takes at least four generations to 'refresh' a name," she says. "As parents, we find the names of our own generation too ordinary, our parents' names too boring and our grandparents' too old. But once we reach our great-grandparents, things start to get interesting." Some of today's most stylish names, she adds, would sound right at home in a Victorian nursery.

Of course, while parents will mull over the trends, most will find their actual pick is much more personal.

Sharon Johnson and her husband, Martin, named their son, now 4, True Solomon and their daughter, now 11/2, Honor Psalm. "We thought about the virtues we wanted to instill in our children," writes Sharon, a District homemaker, in an e-mail. "We knew instantly that True and Honor were right -- their names would be a steadfast reminder of the type of character we wanted them to have. How terribly ironic if our daughter were not honest or honorable and our son were not true or trustworthy in their adult lives."

Heather Martin, a stay-at-home mom from Alexandria, factored humor into the names she and husband Jeff chose for their two sons, a toddler and a baby born in March.

"Charles and Gordon are good strong names for men, but little boys named Charlie and Gordy just crack us up. Isn't that what it's all about, really?" she asks.

And good humor is a great characteristic to bring to the entire process. A name, after all, doesn't have to be destiny.

In "Freakonomics," Levitt relates the tale of two brothers, who for reasons now forgotten were named Winner and Loser. Loser, it turned out, scored a scholarship to prep school, attended college and became a well-regarded police sergeant. Winner? He's unfortunately amassed a long criminal history.