We were using it as kids in the '50s. It's still useful, but like any other word can be overused.
John
cool
O.E. col, from P.Gmc. *koluz, from PIE base *gel- "cold, to freeze." The v. form kele (from O.E. colian) was used by Shakespeare, but has been assimilated with the adj. into the modern word. Applied since 1728 to large sums of money to give emphasis to amount. Meaning "calmly audacious" is from 1825. Slang use for "fashionable" is 1933, originally Black English, said to have been popularized in jazz circles by tenor saxophonist Lester Young. Coolant in the radiator sense is from 1930. Coolth, on model of warmth, is occasionally attested since 1547, and was used by Pound, Tolkien, Kipling, etc.