1706, "register of deaths, a list of the dead," from Medieval Latin obituarius "a record of the death of a person," literally "pertaining to death," from Latin obitus "departure, a going to meet, encounter" (a euphemism for "death"), from stem of obire "go toward, go to meet" (as in mortem obire "meet death"), from ob "toward" (see ob-) + ire "to go" (from PIE root *ei- "to go").
Meaning "a record or announcement of a death," especially in a newspaper, and including a brief biographical sketch, is from 1738. As an adjective, "relating to or recording a death," from 1828. A similar euphemism is in Old English cognate forðfaran "to die," literally "to go forth;" utsið "death," literally "going out, departure."