The expression "Keep it dark" refers to telling someone to keep a secret. The phrase uses the imagery of staying in the dark as something that should remain unseen.
It means to keep them unaware, to keep them from finding out the truth.
keep it under the hat
Nothing - however, keeping a person in the dark means to withhold information from them so that they are unaware of the truth, as if they are stumbling around in the darkness trying to find it.
An excellent expression. To keep an eye, or to keep an eye on things means to maintain a watchful eye. You monitor what is happening with an appropriate zeal to the occasion. Another idiom would be, to keep an eye peeled. It means you are watching and protecting something, or someone.
The idiomatic meaning of keep the pot boiling means to to keep it going actively.
"Keep up the good work" means to continue doing well and maintain a high standard of performance or behavior. It is an encouraging phrase used to motivate someone to persevere and maintain their positive momentum.
A white elephant means 'something useless and expensive to keep'
It is a horse-racing term. If you keep control of a horse's head, you control the way that the horse runs, and how fast it goes. Keeping your head means keeping control of yourself and staying calm in all situations.
Think of someone trying to get out of their backyard and trespassing on someone else's yard. This phrase means "mind your own business and stay out of mine." It's an emphatic order to keep to yourself.
"Keep up the work" really isn't a common idiom, so I don't have another idiom that means the same. Sometimes you hear "keep up the good work," which means to continue doing a good job, to keep on with the quality you're doing now. However, I still can't think of another idiomatic expression that means the same thing...
"Touch base" is typically written as two words. It is used informally to indicate making contact or reconnecting with someone.
I've never heard it used as an idiom, but it sounds as if you are comparing people who habitually take something from you to leeches and should avoid them because they would keep taking from you -- perhaps energy or money.