If you say /asdf a b c d e f then it will call the function serverCmdAsdf(%client, %a, %b, %c, %d, %e, %f) with variables %a through %f as "a" through "f". Each word after the slash command is put into a parameter.
Using this, you can define a %target variable in the serverCmd, then use /whatever TargetName to put "TargetName" into %target.
%target would then be a string of the target's name, not the target itself. To find the target, you use findClientByName with %target as the parameter, and it will return the client object, from which you can use .player to find the player object to kill (if there is one).
An additional note: Variable names do not matter. %victim doesn't magically become the target. You could do %victim = 3.14159; or %victim = findClientByName(%target); ; it doesn't matter that it's called victim, all that matters is what's inside of it. However you should keep your variable names relevant to what they're storing, so its easier for yourself and other people to understand.