to speak
啽 centers on the act of speaking or vocalizing. The given meanings point to speech, but the kanji is rare and its exact nuance is uncertain.
啽 combines 口 (mouth) with 弇, which likely contributes a phonetic element. The exact historical development is uncertain.
The mouth 口 beside 弇 suggests a mouth producing sound. Picture a mouth opening wide to speak, with the right side as the sound waves coming out.
For ガン, imagine a person speaking with a strong, guttural 'gan' sound, like the start of 'gander'. The mouth 口 opens and the sound 'gan' comes out.