Where ha you been looking? The mostobvious place on the internet is Merriam Websyer's online dictionary. Wbster'sis the most prestiious American dictinary. Yu can access itfreat Merriam-Webster Online
Any native speaker would understand 'thick head' but I wouldn't class it a an idiom.
I checked out your firt four examples in MW and found them all although Ihad to search for 'turn turtle (capsize) under 'turn'.
As for phrases like 'worm it out', 'work it out', figure it out , 'think it out', draw it out' 'spin it out', etc, etc. if you can work one of them out for yourself, you will understand all of them.
Think about how a worm makes a hole, twisting and turning and movin a little bit of earth each time until the hole is complete. Imagine your wife/husband trying to extract information from you which you were reluctant to give. She/He'd worm it out of you in the end!
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