c. 1600, "subjugated," past-participle adjective from subdue. Meaning "calmed down, reduced in intensity" is recorded from 1822.
a subdued whisper
children were subdued and silent
subdued lighting
subdued lights and soft music
subdominant
subduce
subduct
subduction
subdue
subdued
subfusc
sub-giant
subgroup
subhead
subhuman