Example: The trick to handling a job interview is to walk in cool as a cucumber and pretend you know what you are talking about.
Origin: "Cool as a cumber" is an alliteration.
Alternatively,
A cut cucumber actually can feel cool to the touch. This is because they are very moist, evaporation of the moisture provides a cooling effect. The bizarre image of woman receiving facial treatments with slices of cucumber on each eye is brought to mind. It is precisely for this cooling effect that this is done.
Example: You will not lose weight until you give up chocolate, and I suggest you go cold turkey.
Origin: The expression originates from the goose bumps and palor which accompany withdrawal from narcotics or tobacco. One's skin resembles that of a plucked, cold turkey....
Example: Sit down, have a beer, and let's chew the fat.
Origin: The Inuit (different from Eskimos) used to chew on pieces of whale blubber almost like chewing gum. The blubber took quite a while to dissolve, so it just sort of helped pass the time while they were doing something else. Some other cultures may have used bacon fat in a similar way.