kaḥash

This word is a noun, so it names the falsehood itself rather than the act of telling it. Hebrew has several words in this area, and this one leans toward deception as something people produce and then live on. Hosea can speak of a nation eating the harvest of it (Hosea 10:13), and Nahum can sum up a whole city with it (Nahum 3:1).

The range runs from particular lying words to a settled untrustworthiness:

• lies spoken by people who curse and slander an enemy (Psalm 59:12)
• flattering falsehoods that keep a king and his officials pleased (Hosea 7:3)
• a nation's faithlessness toward God, standing next to another word for treachery (מִרְמָה) in Hosea 11:12

That second edge is what makes the word worth noticing. Where the common Hebrew word for a lie (שֶׁקֶר) can name any single untruth, this one keeps landing on people and nations whose whole dealing has gone false, which is why four of its six appearances stand in prophets accusing Israel or Nineveh.

The root behind this word runs in two directions. The related verb (כָּחַשׁ) can mean to lie to someone, and it can also mean to shrink and fail, as when a psalmist says his flesh has grown lean from going without food. The noun follows the same double track, and in Job 16:8 most readers take it in the second direction.

Job pictures his own body in a courtroom. God has shriveled him up, and his gaunt frame now stands and testifies against him to his face, because his friends read his ruined health as proof that he has sinned. The wasted body becomes the accuser. Some scholars keep the word's usual sense of falsehood here instead and take Job's affliction itself as the lying witness.