Full Idea
Holism says that nothing that can be said in one language can be said in another one. The expressibility hypothesis says that everything that can be said in one language can be said in every other one.
Gist of Idea
Holism says language can't be translated; the expressibility hypothesis says everything can
Source
Thomas Hofweber (Inexpressible Properties and Propositions [2006], 6.4)
Book Reference
'Oxford Studies in Metaphysics vol.2', ed/tr. Zimmerman,Dean W. [OUP 2006], p.203
A Reaction
Obviously expressibility would only refer to reasonably comprehensive languages (with basic logical connectives, for example). Personally I vote for the expressibility hypothesis, which Hofweber seems to favour.