Origin

The character combines the thread radical 糸 on the left, which points to the core meaning of something made from fibers, with a sound component 丩 on the right that hints at the pronunciation. The image of threads being twisted together led to the meaning "twist," and from there the character came to mean investigating or examining something thoroughly, as if you were unraveling and checking the threads carefully. The native Japanese reading ただ.す preserves this sense of setting something straight or correcting it through careful scrutiny.