decease (n.)

"death," early 14c., from Old French deces (12c., Modern French décès) "decease, death," from Latin decessus "death" (euphemism for mors), also "a retirement, a departure," from decess-, past participle stem of decedere "die, depart, withdraw," literally "to go down," from de "away" (see de-) + cedere "to go" (from PIE root *ked- "to go, yield"). Still used with a tinge of euphemism.

"to die, depart from life," early 15c., decesen, from decease (n.). Related: Deceased; deceasing.