Full Idea
Frege appealed to definition, or (if 'meaning' is preserved) synonymy: the non-logical analytic truths can be converted to logical truths by substitution of definitions for defined terms, or synonyms for synonyms.
Gist of Idea
All analytic truths can become logical truths, by substituting definitions or synonyms
Source
report of Gottlob Frege (Grundlagen der Arithmetik (Foundations) [1884], §005, 88) by Georges Rey - The Analytic/Synthetic Distinction 1.2
Book Reference
'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.3
A Reaction
This is a 'dogma of empiricism' attacked by Quine. It seems rather obvious (with hindsight?) that you can smuggle whatever is required to do the job into your definition. Or assert some slightly dubious synonymy.
Related Idea
Idea 7317 'Renate' and 'cordate' have identical extensions, but are not synonymous [Quine, by Miller,A]