哈
ゴウ, ハ, ソウ
school of fish, fish's mouth moving, exhaling sound
JLPT0 G13 S0 F5000
As per 合# (press/fit together) + 口 mouth → press the lips together in sucking in air (compare 吸, 歙 and 噏). The *opening and closing of a fish's mouth* is a borrowed meaning → *school of fish*.
[Full Kanji Etymology List]