Fawning on someone means to excessively flatter or suck up to them. There are several synonyms that can be used in place of the term 'fawns on.' One alternative is 'grovels,' which also suggests a sense of subservience. Another option is 'ingratiates,' which implies that the person is trying to win favors or get on someone's good side. A third synonym is 'sycophants,' which refers to individuals who seek to gain advantage by excessive flattery. Other synonyms for 'fawns on' include 'flatters,' 'kowtows,' 'curries favor,' and 'sucks up.' Ultimately, all of these synonyms suggest that the person is trying to gain favor through insincere and excessive flattery.