c. 1300, "declaration of hostile intent," also (early 14c.) "a threat or act of threatening," from Old French menace "menace, threat" (9c.), from Vulgar Latin minacia "threat, menace" (also source of Spanish amenaza, Italian minaccia), singular of Latin minaciæ "threatening things," from minax (genitive minacis) "threatening," from minari "threaten; jut, project," from minæ "threats; projecting points," from PIE root *men- (2) "to project." Applied to persons from 1936.
c. 1300, manacen, "to threaten, express a hostile intention toward," from Old French menacier "to threaten; urge" (11c.), Anglo-French manasser, from Vulgar Latin *minaciare "to threaten," from minacia "menace, threat" (see menace (n.)). Intransitive sense of "to be threatening, pose a threat of danger or harm" (of abstractions or objects) is from mid-14c. Related: Menaced; menacing.
Threaten is of very general application, in both great and little things: as, to be threatened with a cold; a threatening cloud; to threaten an attack along the whole line. Threaten is used with infinitives, especially of action, but menace is not; as, to threaten to come, to punish. Menace belongs to dignified style and matters of moment. [Century Dictionary]