The delectable little Dutch songs with which she used to dulcify the house grew less and less frequent, and she would forget her sewing, and look wistfully in her father’s face as he sat pondering by the fireside.
-- Washington Irving, “Wolfert Webber, or Golden Dreams,” Tales of a Traveller, by Geoffrey Crayon, Gent., 1824
Time had not dulcified the tempers of the three elder.
-- William Blackwood, Blackwood's Edinburgh Magazine, 1831
Dulcify is derived from the Latin word dulcis meaning "sweet." It entered English around 1600.