interpolate

Concise Oxford English Dictionary © 2008 Oxford University Press:
interpolate /ɪnˈtəːpəleɪt/

▶verb

• 1 insert (words) in a book, especially to give a false impression as to its date.

  ■ make such insertions in (a book).

• 2 interject (a remark) in a conversation.

• 3 Mathematics insert (an intermediate term) into a series by estimating or calculating it from surrounding known values.

– derivatives
interpolation noun,
interpolative adjective,
interpolator noun.

– origin C17: from L. interpolat-, interpolare ‘refurbish, alter’, from inter- ‘between’ + -polare (rel. to polire ‘to polish’).