early 12c., coroune, croune, "royal crown, ornament for the head as a symbol of sovereignty," from Anglo-French coroune, Old French corone (13c., Modern French couronne) and directly from Latin corona "crown," originally "wreath, garland," related to Greek korone "anything curved, a kind of crown," from suffixed form of PIE root *sker- (2) "to turn, bend." Old English used corona, directly from Latin.
Figuratively, "regal power," from c. 1200. From late 14c. as "a crowning honor or distinction." From c. 1300 as "top part of the skull or head;" from 1670s as "top of a hat." From 1804 as "part of a tooth which appears above the gum."
Extended late 14c. to "coin bearing the imprint of a crown or a crowned head," especially the British silver 5-shilling piece. Also the name of monetary units in Iceland, Sweden (krona), Norway, Denmark (krone), and formerly in German Empire and Austria-Hungary (krone).
Crown of thorns was late Old English þornene crune.