Full Idea
Since sounds are voluntary and indifferent signs of any idea, a man may use what words he pleases to signify his own ideas to himself.
Gist of Idea
Since words are just conventional, we can represent our own ideas with any words we please
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 3.09.02)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.476
A Reaction
Evidently not in tune with Wittgenstein, but it is obvious that I could invent any word I like for my favourite temperature for tomato soup.