知り合い
しりあい · shiriai · JLPT N2 · noun
acquaintance
知り合い: 知る (to know) + 合う (to meet, to match) = people who have met and so know each other a little
知る means to know and 合う means to meet or fit together. Two people who have met and become known to each other are 知り合い, a step short of a close friend.
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.