Trefoil
三つ葉 mitsuba

A three-leaf motif. As a crest, the related katabami (wood sorrel) stands for family prosperity because it spreads so vigorously.
Plant crests (kamon) from the mid-Heian period; katabami among the five most common crests
Family crests emerged in the mid-Heian period on nobles' oxcarts and clothing, spread to samurai, merchants and kabuki actors, and by the Genroku era (1688–1704) were widespread among commoners. The three-leaf katabami (wood sorrel) is one of the 'five great crests' because so many families use it; it is usually explained as a wish for descendants to spread like the plant.
Three-leaf designs appear as crests and as light repeats on modern textiles.