LW uses this expression in the course of clarifying the meaning of critical terms in the context of various philosophical arguments. His is a very useful rhetorical move which often illuminates what is problematic about the argument at issue. In making this move, LW asks us to remember our ordinary use of the pivotal term, its 'home', where it works best. The choice to move ahead is ours. We can create new meanings but then face the sanctions and restrictions of our discourse community.
Meaning is independent of use.
A theory explains X in terms of Y, where X and Y are distinctly different. So, one doesn't explain the action of sleeping pills by refering to their dormative properties, nor ones strange adult behavior by pointing to ones strange childhood, unless one can specify the mechanism of action for bring about sleeping or strangeness. Well, it sounds that way at first blush. I learn new meanings in the context of use. I demonstrate the meaning of a word by using it.