Mechthild is the German form of Matilda — Old German maht (might) and hild (battle), "mighty in battle." Mechthild of Magdeburg (c. 1207-1282) was the German Beguine mystic whose Flowing Light of the Godhead is one of the masterpieces of medieval Christian mysticism.
Mechthild of Hackeborn (1240-1298) was her younger Cistercian counterpart.
Mechthild is a compound name. Its parts are hild — each an attested element with a recorded meaning of its own.
Mechthild 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 Mechthild reduce to 1, The Leader. This is a traditional interpretive system, not a factual claim about the name.