What morphological features suggested the epithet "bifrons" in Rubus bifrons? The scientific name of the familiar invading species "Himalayan Blackberry" (or "European Blackberry" or "Armenian Blackberry") in the US is Rubus bifrons (with Rubus armeniacus as an alternative if the two species are considered same).
As @acvill pointed out, R. bifrons was named in 1821 by Lorenz Chrysanth von Vest. The original description can be found here (pages 163-164).
The latin bifrons translates to "two faces". I'm not sure, but I suspect this references the leaves of the plant, with the upper surfaces being dark green and the lower white (or much lighter)
Foliis subrotundo-ovatis subtus albentibus saepe villosis, tenue et confertim serratis...
[Leaves roundish-ovate, whitish on the underside, often villous thin and serrate...]
However, I can't translate his comments after the description, so maybe there is another explanation included there.