The generic name honours Finnish lichenologist Veli Räsänen,[1] who described the type species as Phacopsis huuskonenii in 1948.

The type specimen was collected by botanist Avi Johannes Huuskonen from Pielavesi (North Savo, Finland), where it was found on the thallus of the lichen now known as Bryoria implexa.

[2] In 2017, Divakar and colleagues used a then-recently developed "temporal phylogenetic" approach to identify temporal bands for specific taxonomic ranks in the family Parmeliaceae, suggesting that groups of species that diverged within the time window of 29.45–32.55 million years ago represent genera.

[3] This synonymy was not accepted by Robert Lücking in a later critical analysis of this technique for lichen systematics, who noted that "if taxonomy and classification are to reflect evolutionary history, then merging them into a single genus just because of the point in time they diverged is certainly not justified".

[4] Raesaenenia is characterized by having an ascus structurally similar to those of genus Phacopsis, but with somewhat cylindrical ascospores that have thickened caps of wall tissue at each end.