The range of significance in Type Theory
Comes from Russell, and it's actually about the domain, not the codomain, if I understand ol' Bertie correctly. A propositional function like "x>3" only has significance if we limit the possible values of x to numbers.  Today we would call that the domain, but his choice of words is defensible: the range of significance of a propositional fn  is the set of values that make it meaningful - i.e. true or false - as opposed to meaningless nonsense, like "Pegasus>3".  The range of significance of a numeric fn is the set of values for which it yields a value, rather than crashing, so to speak.

The relation to types is fairly obvious: the range of significance of a fn $f: A\rightarrow B$ is just the "values" of type $A$ to which $f$ can be meaningfully applied.  The concept and term "type" is just a more commodious way of expressing the same basic concept.  Google "propositional function range of significance" and you'll get links to his original paper and lots more.