Why are introns called 'introns' when they are the actual ones who are getting spliced out from the pre-mRNA. Shouldn't exons be named introns as they are the ones that are 'in' and are not 'exiting'? On what criteria were they named like this?
Introns are the intragenic regions and exons are the regions which are expressed.
This is the relevant passage in full:
The notion of the cistron, the genetic unit of function that one thought corresponded to a polypeptide chain, now must be replaced by that of a transcription unit containing regions which will be lost from the mature messenger - which I suggest we call introns (for intragenic regions) - alternating with regions which will be expressed - exons. The gene is a mosaic: expressed sequences held in a matrix of silent DNA, an intronic matrix.
Well, as this question seems to be about helping the X- or M- generations get to grips with baby boomer terminology, let me explain how I remember what introns are.
Before Gilbert coined the term (as @xusr explains) original reports of the research that established the mosaic nature of eukaryotic genes refered to
For example, there was a paper from Phil Leder’s lab in 1978 entitled
Intervening sequence of DNA identified in the structural portion of amouse β-globin gene
So intron was really related to intervening in its origin, and knowning this it is easy to remember which is which — introns and exons.