means A short, catchy phrase used to sum up and sell an idea, brand, or cause in a memorable burst.

from From Scottish Gaelic 'sluagh-ghairm' — literally 'army cry' — built from 'sluagh' (host, army) and 'gairm' (shout or call). It began as a clan's battle-cry on the Highland field, the words you screamed charging downhill, before it mellowed over the centuries into the words a company murmurs in your ear to sell you toothpaste.