euthanasia (n.) Look up euthanasia at Dictionary.com
1640s, "a gentle and easy death," from Greek euthanasia "an easy or happy death," from eu- "good" (see eu-) + thanatos "death" (see thanatology). Slightly earlier in anglicized form euthanasy (1630s). Sense of "legally sanctioned mercy killing" is recorded in English by 1869.