is a common military term meaning kilometer
when referring to distance. Its use became popular among US
soldiers in Vietnam
during the 1960s, although veterans
of the war recall its usage as early as the 1950s. The term is of unknown origin. It is likely to be an example of condensed pronunciation
of the term kilometer
, although other theories exist.
Click (with same pronunciation but spelled with "c" instead of a "k") is another military term meaning one minute of arc when adjusting the sighting system on a weapon such as a rifle.