double

double at the double at running speed; very fast.
double Dutch language that is impossible to understand, gibberish. The term is recorded from the late 19th century, although high Dutch, in the same sense, is earlier.
double helix a pair of parallel helices intertwined about a common axis, especially that in the structure of the DNA molecule; the structure was originally proposed by Francis Crick (1916–2004) and James D. Watson (1928– ), broadly explaining how genetic information is carried in living organisms and how genes replicate.
double or quits (in the US, double or nothing) a gamble to decide whether a loss or debt should be doubled or cancelled.
doublethink the acceptance of or mental capacity to accept contrary opinions or beliefs at the same time, especially as a result of political indoctrination, coined by George Orwell in his novel Nineteen Eighty-Four (1949).
double whammy a twofold blow or setback; a figurative use of ‘two blows resulting in a knockout’. The original (US) sense of whammy was ‘an evil influence’, and in the 1950s was particularly associated with the comic strip L'il Abner; a double whammy in this context was an intense and powerful look which had a stunning effect on its victims.

Double whammy in its current sense entered the language through modern politics, being given a high profile by Conservative campaigning in the British general election of 1992, with campaign posters on tax policy using the slogan, ‘Labour's double whammy’.