错 cuò = 钅 (jīn, metal) + 昔 (xī, the phonetic). A pictophonetic compound of the left-hand metal radical 钅, the compressed form of 金 used down the side of a character, with 昔 on the right carrying the sound (xī, which over time shifted to cuò). The traditional form 錯 writes the radical out in full as 金. The metal radical is no accident: the earliest documented meaning, recorded in the Shuōwén, is metalwork.

That first sense was inlay and plating: 金错刀, the "gold-inlaid blade," names coins and weapons whose surfaces were grooved and filled with threads of gold, the bright metal crossing through the darker base. From inlay the word reached toward the file and the whetstone, the grinding of one hard surface against another. The 昔 on the right, whose own picture is sun over piled, stacked layers, suits a character built from crossing, layered lines of metal.

The leap to the modern senses runs through the idea of crossing. Threads of inlay cross and interlace; from there 错 came to mean interlocking, intersecting, set crosswise (错综 cuòzōng, intricate; 交错 jiāocuò, to interlace). When lines cross where they should run straight, they have gone awry, and that is the everyday sense today: 错 as wrong, mistaken, in error. The thing that does not line up.

The most useful turn 错 takes is negation. 没错 méicuò, "no error," is the warm everyday way to say "that's right, exactly." And 不错 búcuò, literally "not wrong," is the workhorse compliment of spoken Chinese: it means "pretty good, not bad at all," and lands as genuine praise rather than faint approval. 这家饭馆不错 "this restaurant is quite good" is a recommendation, not a hesitation.

The logic is the same one that made 错 mean error in the first place. If error is what crosses where it should run straight, then "no crossing" is the line running true. To be 不错 is to have nothing out of place, and Chinese hears that absence of fault as a quiet, reliable yes.

Picture a craftsman cutting fine grooves into a dark bronze blade and pressing threads of gold into them, 钅, the metal radical down the left. The gold lines cross and interlace over the metal, bright over dark. That crossing of metal is the literal heart of 错: inlay, the lines that lay across one another.

Now let one thread slip out of its groove and cross where it should have run straight. The pattern is spoiled; the line has gone wrong. That single crossed line is the everyday 错: a wrong character, a wrong turn, a mistaken answer, the thing that does not line up. To say 错了 is to point at the thread that went astray.

The same image runs the other way too. Two travelers walk crossing paths at a station and slip past without meeting: they 错过 each other. And a thing with not one thread out of place is 不错, "not wrong," which Chinese hears as quiet praise. Hold the gold inlay in mind, and wrong, missed, and not bad all trace back to one set of crossing lines.