zero, spill, overflow, nothing, cipher
零 centers on the idea of emptiness or absence: zero, nothing, or a cipher. The spill and overflow senses are natural extensions—when something is empty, it can no longer contain, so liquid spills over.
零 combines 雨 (rain) with 令, which likely contributes the sound. The original meaning is associated with light rain or drizzle, which later extended to the idea of a small amount, and eventually to zero or nothing.
Rain 雨 falls on an empty order 令: when there is nothing to order, you have zero. The rain spills over the empty form, like an overflow from nothing.
For レイ, imagine a ray of light shining on a zero: ray -> レイ, and the zero becomes visible in the rain.
zero; nought
waste-water container (tea ceremony)
to spill; to drop; to shed (tears)
insignificant; trifling; paltry; cottage (industry); tiny (company)
spilling; spill
below zero; sub-zero
leavings; leftovers
nilpotent
nilpotent element
midnight; 12am
noon; 12pm
to boil over
penny wise and pound foolish
absolute zero
gripe session; grievance session
to spill; to fall out of; to overflow
unexpected piece of good luck; windfall
bulbil (esp. of a Japanese yam); propagule; brood bud
Laportea bulbifera (species of nettle-like plant)
alpine bistort (Bistorta vivipara)