early 15c. (of church buildings) "set apart and consecrate to a deity or a sacred purpose," from Latin dedicatus, past participle of dedicare "consecrate, proclaim, affirm, set apart," from de "away" (see de-) + dicare "proclaim" (from PIE root *deik- "to show," also "pronounce solemnly").
General sense of "devote with solemnity or earnest purpose" is from 1550s. Meaning "ascribe or address (a literary or musical composition) to someone or something" is from 1540s. Related: Dedicated; dedicating.