just barely
—Because Tom left work late, he caught the last bus only by the skin of his teeth.

Job lost everything he had and was so near death he said,

My bones stick to my skin and my flesh;
I have escaped alive with only the skin of my teeth. (Job 19:20)

The skin of one’s teeth originally referred to the gums surrounding the teeth. While this certainly is not much skin, many people think of the modern skin of one’s teeth as meaning “the skin on the teeth,” which is no skin at all. The more common usage of the phrase (using by rather than with), shifts the meaning more towards escaping harm by the smallest of margins.

Later, Job responded to the men who thought they knew the cause of his suffering, calling that cause “the root of the matter.” He warned them to be careful about God’s judgment in their own lives:

If you say, “How we will pursue him,
since the root of the trouble [root of the matter—KJV] is found in him!”
Fear the sword yourselves,
for wrath brings the punishment by the sword,
so that you may know
that there is judgment.” (Job 19:28,29)

Today, root of the matter means “the main part or cause of something.”