CROON

Croon (kro͞on), v. i. [[OE. croinen, cf. D. kreunen to moan. √24.]] 1. 1. To make a continuous hollow moan, as cattle do when in pain. Jamieson.
2. 2. To hum or sing in a low tone; to murmur softly.
Here an old grandmother was crooning over a sick child, and rocking it to and fro. Dickens.