Know why cattywampus was trending last week?
1720, Scottish, "magic, enchantment" (especially in phrase to cast the glamor), a variant of Scottish gramarye "magic, enchantment, spell," alteration of English grammar (q.v.) with a medieval sense of "any sort of scholarship, especially occult learning." Popularized by the writings of Sir Walter Scott (1771-1832). Sense of "magical beauty, alluring charm" first recorded 1840.
1814, from glamour (n.). Related: Glamoured; glamouring.