Why have certain Irish names, like Cornelius and Bridget, practically vanished over the past century and others, like Sean and Aoife, have taken such firm root in Ireland?

This is what a new RTE documentary entitled “One Hundred Years of Names” set out to investigate, and the answers are fascinating.

Documentary filmmaker Sarah Binchy visited Dublin’s Rotunda Maternity Hospital, the Central Statistics office in Cork and Ireland’s National Archives to compare popular names in Ireland, past and present.

When it comes to naming babies in Ireland, it seems that around 80 percent of parents go for tradition, while 20 percent, particularly younger mums, go with trends.

This 20 percent is on the rise, hence the increase in popularity of names from soap operas and movies.

For instance, after “Mamma Mia!” hit theaters in 2008, the name “Sophie” became one of the most common baby names in Ireland.

It seems that parents are taking more liberties with girls’ names than boys’. Aoife is the only traditional Irish name in the top 10 for girls today, with names like Emma, Ella and Katie dominating the name game.

Meanwhile, the popularity of certain boys’ names has been steady for years. The most popular boy names in Ireland in 1998 – Conor, Sean, Jack and James – were still in the top 10 in 2007.

However, though trendy names come and go in Ireland, the documentary notes that Irish names with complex spellings are on the rise for both boys and girls.

Orla has long been a popular name in Ireland, but Irish parents today are opting for “Orlaith,” a more complicated Irish spelling, instead.

Fionn (pronounced Finn) and Cian are complex boys’ names on the rise.

“We called him Fionn,” one woman in the Rotunda said. “Not many boys are called Fionn. And he’s a little warrior, like Fionn McCool.”

One type of name completely disappearing is the saint’s name.

Both Irish names (think “Eamon” instead of “Edward,” or “Seamus” instead of “James”) and saints’ names (like the Irish patron saint Bridget) that didn’t exist in Ireland during the 19th century were on the rise in 20th century as part of the Gaelic Revival and de Valera’s strict Catholic Ireland.

Girls’ names like Bernadette, Carmel, Colette, Magella, Concepta and Imelda – all of which are related to the Catholic Church – became especially popular in the 1950s. But today you’d be hard-pressed to find someone under the age of 40 with such a name.

The naming trend in Ireland has many interesting implications for the changing face of the country.

While Catholic names may be disappearing, and pop culture names are taking their place, one thing’s for certain: names with a strong Irish identity are here to stay.