night, evening, late
晚 centers on the later part of the day: evening, night, and by extension anything that comes late.
晚 combines 日 (sun) with 免, which likely contributes the sound. The character originally referred to the sun setting and the coming of evening.
The sun 日 sets and the right side 免 looks like a person stretching after a long day, signaling evening and night.
For バン, imagine a van arriving late in the evening: van -> バン, and the sun has already set.