Also see definition of "By And By" in Word Study
By and by [ebd]
immediately (Matt. 13:21; R.V., "straightway;" Luke 21:9).
BY AND BY [isbe]
BY AND BY - In the sense of "immediately" is the King James Version translation of exautes, of Mk 6:25 (the American Standard Revised Version "forthwith"); of euthus, Mt 13:21 (the American Standard Revised Version "straightway"); of eutheos, Lk 17:7 (the American Standard Revised Version "straightway"); 21:9 (the American Standard Revised Version "immediately"). In English literally this meaning is obsolete (compare: "After you have dyned and supte, laboure not by and by after, but make a pause--the space of an howre or more with some pastyme" (Babees Book, EETS, 247).
Also see definition of "By And By" in Word Study