The Dutch word for button is
knoop

Dutch Definition

knoop	©
1. n-m. button (knob or small disc serving as a fastener)
2. n-m. knot (i.e. a loop of string or any other long flexible material which cannot be untied without pulling part of the string through the loops)
Ik zit in de knoop. - I'm in a hard spot. / I'm all tied up.
3. n-m. (mathematics) knot
4. n-m. (nautical) knot (i.e. a unit of velocity, corresponding to traveling a distance of 1 nautical mile per hour)
5. n-m. (botany) node, joint
6. v. first-person singular present indicative of knopen
7. v. imperative of knopen

knop	©
1. n-m. a knob, roundish handle, ornament etc.
2. n-m. a button, control device to push etc.; metonymy: control, power to stop
3. n-m. a bud on a (growing) plant

toets	©
1. n-f. button, key (on a keyboard or other input device)
2. n-f. fingerboard (e.g. on a violin)
3. n-f. test, examination
4. v. first-person present indicative of toetsen
5. v. imperative of toetsen