1590s, "injurious to health," from un- (1) "not" + healthy (adj.). Earlier unhealthsome (1540s), unhealthful (1570s). Of persons, "sickly," it is attested from 1610s. Related: Unhealthily.
unhealthy ulcers
an unhealthy diet of fast foods
an unhealthy climate
unhappily
unhappiness
unhappy
unharmed
unharness
unhealthy
unheard
unheeded
unhelpful
unheralded
unhindered
