crool

Imitative.

crool (third-person singular simple present crools, present participle crooling, simple past and past participle crooled)

1. (archaic, intransitive) To murmur or mutter.
   • 1873, Thomas Cooper, The Paradise of Martyrs

     I […] lay down to rest / Upon a grassy hillock, o'er which bowed / A bush in which some late bird kept her nest. / And, as she crooled, I slept.

• color, corol