合わせる
あわせる · awaseru · JLPT N3 · verb-ichidan
to combine
🧩 合う (to fit) + -せる (make) = make things fit together
合わせる is the transitive partner of 合う, to fit or match. The -せる ending turns it into make it fit. The kanji 合 is a lid (亼) sitting on a box opening (口), two parts that close together. 手を合わせる means to put your palms together.
合 — 乛 (lid/roof) + 口 (mouth)
Originally a pictograph of a lidded vessel — a cover (亼) closing over an opening (口) — giving the core sense of 'come together, join, fit.' From 'fit/match' it extended to 'combine, unite, agree' and to measure-word uses. The reading hé reflects this 'joining' meaning.