Tijana is from the Serbian Tijana (Тијана) — South Slavic diminutive of Hristijana (Christiana / Christian woman). Tijana is one of the Serbian + Bosnian + Macedonian feminine names of the late 20th + 21st century. Slavic feminine name reflecting Eastern Orthodox heritage.
Tijana 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 Tijana reduce to 1, The Leader. This is a traditional interpretive system, not a factual claim about the name.