徐 means 'gradually'

This bundle presents life at a range of speeds. Two essays focus on gradual change—for better and for worse—in everything from health to the economy. By contrast, three essays touch on sudden developments, including the outbreak of war, a surge of energy, the rapid rise of subcultures, getting an erection, standing up abruptly, bursts of wit, quick enlightenment, and sudden death. Tying these extremes together, 頓 runs the gamut; when it means "to stay in place" or "stop," this kanji involves setbacks and stalemates, but as "sudden" it pops up in words for wild, crazy behavior.