Galla is from the Latin Gallus — "a Gaul." Galla Placidia (388-450) was the Western Roman empress — daughter of Theodosius I, captured by the Visigoths under Alaric, married Alaric's successor Athaulf, and later ruled as regent for her son Valentinian III. Her mausoleum in Ravenna is a UNESCO masterpiece.
Featured in Gibbon's Decline and Fall.
Galla does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
In Pythagorean numerology the letters of Galla reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.