From Middle English chirmen (“to chirp, twitter”), from Old English ċirman (“to make a noise, cry out, shout”), from Proto-West Germanic *karmijan (“to make a sound”).
The noun is from Middle English chirm (“the call of various birds; chirping”), from Old English ċirm, ċyrm, ċierm (“noise, cry, alarm”), from Proto-West Germanic *karmi, *karm, from Proto-Germanic *karmaz, *karmiz. Doublet of charm (“sound, voices; group, flock”).