Left mouth radical - the indexing component, marking 咱 as a pronoun rooted in spoken speech rather than writing. Same radical anchors other colloquial particles and pronouns (啊, 呀, 嗯), reinforcing the conversational register.
Right side gives both sound and meaning: 自 (self) drifts colloquially toward zán, while its meaning of 'self' fits perfectly - mouth + self adds up to the inclusive 'us,' the 我们 that pulls speaker and listener into one shared self.
