late 14c., "pleasing to the imagination; dishonestly pleasing; having a false appearance of favorableness," present-participle adjective from flatter. Meaning "gratifying to self-esteem" is from 1757. Related: Flatteringly.
a flattering color
flatness
flats
flatten
flatter
flatterer
flattering
flattery
flat-top
flatulence
flatulent
flatus