nothingness, none, ain't, nothing, nil, not
無 centers on absence or negation: the state of nothingness, having none of something, or simply not being the case. The colloquial "ain't" fits as a strong informal negation.
nonexistent; not being (there)
free (of charge); gratuitous
unreasonable; unnatural; unjustifiable
nothing; naught; nought; nil; zero
futility; waste; uselessness; pointlessness; idleness
without
safety; security; peace; quiet
disregarding; ignoring
to be lost (e.g. luggage); to be missing
radio (communication)
infinity; infinitude; eternity
unmanned; uninhabited; unattended; deserted
invalid; void; ineffective; unavailable
without compensation; without reward; without pay
innocence; being not guilty
absence of permission; lack of permission
existence or nonexistence; presence or absence
invincible; unrivaled; unrivalled; matchless; unbeatable; undefeatable
absurd; unreasonable; ridiculous
forcibly; by force; against one's will
to lose (something)
useless; futile
nonexistent; nil; none; nothing (at all); bugger-all
without an occupation; unemployed; jobless
無 originally depicted a person with decorative headdress, associated with dancing, and was later borrowed to express negation or nothingness. The modern form retains the stylized upper shape with 灬 (fire) at the bottom, though the fire component is not historically motivated.
The top looks like a crowded, tangled mess, and the bottom is fire 灬. Imagine a fire burning everything away until there is nothing left: 無 is nothingness.
For ム, imagine a silent movie where nothing makes a sound: the word "mute" captures the idea of nothingness, and "mute" -> ム.