Meaning: To go to bed, to retire for the evening to sleep.
Example: Man, am I bushed, I'm going to hit the sack.
Origin: Although fallen out of common usage, one definition of a sack is a bed. Early mattresses were often made from a cloth sack stuffed with hay, hair, or some other form of padding. In fact "sack out" is defined as "to go to bed, to go to sleep".
Meaning: To go all out, willing to do whatever is required to achieve ones objective.
Example: The Indy cars rounded turn one, hell bent for leather.
Origin: This is a combination of two separate phrases with similar meanings. "Hell bent" meaning to do everything possible to achieve a goal. And "Hell for leather" meaning to do something with vigor or (especially travel) at full speed.
To have a bent is to be determined, as in bent on doing something. Hell is often used in terms associated with high speed and determination (e.g.. "go like hell", "running like hell"). "Hell bent" means to be highly or stubbornly determined.
"Hell for leather" is more literal. In this case "leather" refers to the bridal and saddle on a horse. To ride very quickly is rough on the bridal, stirrups, and saddle and is literally "hell for leather".
"Hell bent for leather" then is to ride very fast and very determined.
Meaning: Common sense, able to stand the test of reasonableness.
Example: If your going to spend your time working anyway, it only makes horse sense to get a high paying job.
Origin: Horses are intelligent animals. They demonstrate the ability act sensibly and to avoid situations that might cause them harm such as taking a fall, hence good common sense.
Example: Bush and Reagan are both credible, but Bush Jr. is a horse of a different color.
Origin: Horses are registered at birth and the registration includes a record of their color. When a horse trades hands due to sale, the registration is also transferred. Sometimes the color recorded on the registration may not match the actual color of the horse leading one to suspect the horse is not the one in the registration.
Horses sometimes change color as they age, just as some people's hair changes color. More likely the horse is not the one represented on the registration but is actually an entirely different horse.
Example: If you choose to live high on the hog, you will be low in the wallet.
Origin: The best meat is on the upper portion of the pig. Rich people have always been afforded this luxury while the servants, slaves and poor have always had to eat pig's feet, chitterlings, cracklings, etc. - low on the hog.
