IDIOMS

kernel of truth

(idiomatic) A core accuracy at the heart of a claim or narrative which also contains dubious or fictitious elements.

Example:   There may be a kernel of truth in the story of how George Washington confessed to his father that he chopped down the cherry tree.
1863, "Latin and Cricket," The Albion, A Journal of News, Politics and Literature, New York, vol 41 no 48 (24 Oct), p. 513.
  Whether the Duke of Wellington really said of the Eton playing-fields that it was there that the battle Waterloo was won, may fairly be doubted. The story has many elements of the myth about it; but, like other myths, it has a kernel of truth.
1955, F. Schmidl, "The problem of scientific validation in psycho-analytic interpretation," International Journal of Psycho-Analysis, vol 36 no 2 (Mar/Apr), pp. 105-113.
  This statement will be unacceptable to many biographers and historians, but there seems to be a definite kernel of truth in it.
2003, "The New Season/Film: Big Fish," The New York Times, 7 Sep, p. AR74.
  It's about a young man (Billy Crudup) who tries to distill the true biography of his dying father (Albert Finney) by looking for the kernels of truth in the many tall tales he has told.