I have often found the "Keyword Substitution" selection names in IDEA's CVS dialogs confusing and misleading. IMHO, the names used do not match the terms and names used in the most of the literature in the industry. While I find a couple of IDEA's names confusion, I especially find the "no substitution" name very misleading. When I do a merge between two branches, I want to use a -kk switch, as recommended in section 5.10 Merging and keywords of the Cederqvist manual. This prevents "numerous conflicts during the merge, because [without the -kk switch] the keywords are expanded differently in the revisions which you are merging." Since I tend to think of -kk as either "keywords-only" or "no values" – or possibly "no values substitution" – I often mistakenly select the "no substitution" option in IDEA, with is actually the -kko switch. IMHO, "no substitution" makes no sense as a name for the -ko switch since it does substitute a value for the keyword; it substitutes the "old keyword string". Also, I do not logically associated "compression" with -kk. I suppose one could argue that since it doesn't expand the keyword to the keyword and its value, it compresses it to just the keyword, but IMHO that is not an intuitive thought process. Below is how the keyword modes are described in what I believe to be the most prevalent and reliable sources. All the sources typically have a common word or phrase in their definitions, which I have highlighted.

IDEA current	switch	client help 1	CVS Pocket Ref 2	Cederqvist Manual 3
expansion	kkv	(Default) Substitute keyword and value	Keyword-Value mode	Generate keyword strings using the default form
expansion locker	kkvl	Substitute keyword, value, and locker (if any)	Keyword-Value-Locker mode	Like `-kkv', except that a locker's name is always inserted if the given revision is currently locked.
compression	kk	Substitute keyword only	Keyword-Only mode	Generate only keyword names in keyword strings; omit their values
no substitution	ko	Preserve original string	Old-Contents mode	Generate the old keyword string, present in the working file just before it was checked in.
binary	kb	Mark file as binary	Binary mode	Like `-ko', but also inhibit conversion of line endings between the canonical form in which they are stored in the repository (linefeed only), and the form appropriate to the operating system in use on the client.
replacement	kv	Substitute value only	Value-Only mode	Generate only keyword values for keyword strings.

In the very least, I believe the -kk "compression" and -ko "no substitution" names need to change. I also think the -kv "replacement" name could be improved by changing it. I think the -kkv "expansion" and -kkvl "expansion locker" names work ok, but still would like to see them conform to the cvs client help information. At the very least, it might be nice to add "(CVS Default)" to the expansion name. Also as mention in JIRA IDEA-16043 that I opened, I think the names should show the actual swith to avoid all confusion. Here are my recommendations:

switch	current name	recommended new name	Severity
kkv	expansion	keyword & value (cvs default) -kkv	low
kkvl	expansion locker	keyword & value with locker -kkvl	low
kk	compression	keyword only -kk	high
ko	no substituion	preserve old keyword & value -ko	high
kb	binary	binary -kb	na
kv	replacement	value only -kv	medium

I realize some of the recommended names are a bit long, but I beleive them to be the best choices for matching typical names. References 1) cvs client ouput to command cvs -H admin 2) CVS Pocket Reference Guide, O'Reilly Publishing, ISBN 0-596-00003-0 3) Cederqvist Manual section 12.4 Substitution modes, http://cvshome.org/cvs/manual/cvs-1.12.13/cvs_12.html#SEC103