encajar
/enkaˈxaɾ/ · B1 · verb
to fit, to dovetail
📦🧩 en + caja (box) + -ar = to put into a box, so it fits snugly
Caja means box, from Latin capsa, which also gave English case and capsule. Encajar first meant putting something into its box. It now means anything that fits into place, like a puzzle piece, or an idea that fits: eso no encaja = that doesn't add up.