the.com/leaven

means A substance (like yeast or a bit of fermented dough) that causes a mixture to ferment and expand, or more broadly, a small influence that gradually transforms something larger.

from From Old French 'levain,' rooted in Latin 'levare' meaning 'to raise' or 'lift' — the same root that gives us 'levitate' and 'elevate.' The word has carried a figurative sense since biblical times: the New Testament's 'a little leaven leavens the whole lump' cemented its use as a metaphor for any small force that works invisibly through something bigger, whether that's dough, an idea, or a culture.