谅

Left speech radical (side-form of 言) — anchors 谅 as a verbal act. To forgive is to say words of pardon; to assume is to suppose verbally; to understand is to grant something in speech. The radical groups 谅 with 说 speak, 话 talk, 请 request, 谢 thank — all matters performed through speech.

Right 京 supplies the sound — jīng shifted to liàng through Old Chinese velar/lateral alternation, attested across this phonetic family. 京 itself pictures a tall watchtower or capital gate; the meaning doesn't carry. Same phonetic in 凉 cool, 谅 forgive, 椋 (a tree), 鲸 whale — a tight jīng / liàng / liáng cluster.