Shigeko is from the Japanese 茂子 / 重子 (Shigeko — shige luxuriant/lush/abundant + ko child — luxuriant child, abundant child). Shigeko is one of the Japanese feminine names — central to traditional Japanese heritage.
Shigeko 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 Shigeko reduce to 2, The Peacemaker. This is a traditional interpretive system, not a factual claim about the name.