ziqah

Every time this word means chains, someone has just lost a war. Conquered kings are bound with them in Psalm 149:8, the traders of Egypt and Cush walk past Israel wearing them in Isaiah 45:14, and Nineveh's leading men are bound with them when the city falls in Nahum 3:10. The word never turns up in the singular, so it always pictures a full set of restraints rather than one link.

It also likes company. In almost every verse a second word for bonds stands beside it: iron shackles (כֶּבֶל) in Psalm 149:8, cords of affliction in Job 36:8. That pairing is what makes the sense so secure, and it is also what keeps the word general. It is the plain term for what a prisoner wears, while the words alongside it name the particular piece of hardware.

Job 36:8 is the one place where the chains may not be actual metal. Elihu is describing people whom God has brought to a standstill, and the matching phrase in the line calls their restraints cords of affliction, which turns the chains into a picture of suffering that will not let a person move. A closely related spelling of the same word shows up in Jeremiah 40:1 and Jeremiah 40:4, where the prophet is led away in chains and then set free from them.

Both places where this word means something burning describe fire that a person has set in motion. In Proverbs 26:18 a man shoots them the way an archer shoots, and the very next word in the line is arrows (חֵץ), so these are burning shafts sent at somebody. In Isaiah 50:11 people light a fire, strap the burning pieces to themselves, and then walk by their own glow.

The two pictures are close enough to be one word and different enough to explain why English Bibles disagree. Some print "firebrands", some "flaming arrows", some "sparks", some "torches". What holds the uses together is not the shape of the object but what it does: it burns, it travels, and whoever launched it is answerable for where it lands.

That last point is the sting in both verses. Proverbs is describing a man who hurts his neighbor and then says he was only joking, and Isaiah is describing people who make their own light rather than wait on God in the dark. In each case the fire comes back on the one who lit it.