Summary:

Tooth and nail is a colorful idiom, without reservation, but to fight with all one's power and strength. The phrase was originally a reference to battling an adversary and using one's teeth and nails as weapons: biting with the teeth and scratching with the nails.

Article:

The phrase can be used in many variations:

Fight off a predator (you figure out what kind) tooth and nail

Defend (someone or something) tooth and nail

Try to improve or accomplish something tooth and nail

Oppose ( someone or something tooth and nail

Even positive connotation; I will fight my way to the top tooth and nail with all my power and strength to accomplish my goals and be successful

One's performance or promotion

Striving for justice

Fight for illusions like climate change

Academic achievement

Political competition

Even though it is a corny-sounding phrase, its history goes back to the late 1500s.