façon de parler (n.)
A turn of phrase or rhetorical formula, especially one that ought not to be taken literally, but rather as employed for convenience of expression only. Wiktionary
A way or manner of speaking; a mere phrase or formula.
S. H. Hodgson Let. 8 Apr. in R. B. Perry Thought & Char. W. James (1935) I. 642 What is ‘the mind’?.. I suspect it is a mere façon de parler..which has a basis neither in psychological construction nor in philosophical analysis.
1907 W. De Morgan Alice-for-Short xlii. 439 Which was palpably a lie, taken literally; but was a façon-de-parler that passed muster, taken leniently. OED
Leibniz was well aware of the problems that this raised. His reaction was to urge us not to take talk of infinitesimal quantities literally. We could think of it as just a façon de parler, or as a 'useful fiction', to be justified by appeal to its enormous utility. A. W. Moore; The Infinite (2018)
Let us distinguish in mental phenomena a virtual part implemented by neurophysiological processes and a fictitious part not implemented at all, that is an illusion (or an idealization, or a mere façon de parler) whose introduction in our language sometimes may be quite useful but that strictly speaking does not exist. Oscar Vilarroya et al.; Social Brain Matters (2007)
There are no discrete unities identical to themselves and different from others. Distinguishing between natural kinds is merely façon de parler, referring only to a certain way of perceiving reality. Robert Spaemann; Essays in Anthropology (2010)
On the other hand, I do not know of any significant study of postmodernism that sees it object as a "reality" that is out there, to be discovered and mapped. What may appear as a result of the mimetic illusion is almost always a mere façon de parler, which is based on certain mimetic metaphors (the mind as a mirror, the mirror of nature, etc.) built into our language. M. Calinescu in M. Calinescu and D. Fokkema (eds.); Exploring Postmodernism (1987)
When he says " paranoid streak", he does not really mean the term" paranoid" to be taken seriously—it is just a facon de parler. Stephen Toulmin; The Return to Cosmology (1985)