"un" is French for "one", and fun is a playful English word. For examples of this notation, see, e.g. Le Bruyn (2009), or the links by Le Bruyn, Connes, and Consani. Le Bruyn, Lieven (2009), "(non)commutative f‑un geometry", arXiv:0909.2522 [math.RA]
Lorscheid (2016) Lorscheid, Oliver (2016), "A blueprinted view on F1‑geometry", in Koen, Thas (ed.), Absolute arithmetic and F1‑geometry, European Mathematical Society Publishing House, arXiv:1301.0083
"un" is French for "one", and fun is a playful English word. For examples of this notation, see, e.g. Le Bruyn (2009), or the links by Le Bruyn, Connes, and Consani. Le Bruyn, Lieven (2009), "(non)commutative f‑un geometry", arXiv:0909.2522 [math.RA]