Nabokov's Latin was mostly based in Linnean taxonymy terms.
Although W.T. Stern's standard BOTANICAL LATIN does not specifically give
the term patifolia, PAT- often has the meaning 'broad'. Hence "patifolia"
would mean something like "broad leaf"--a suitable descriptive term for
Kinbote's play pillow.
For other needs
than sleep Charles Xavier had installed in the middle of
> the Persian
rug-covered floor a so-called patifolia, that is, a huge, oval,
luxuriously flounced, swansdown pillow the size of a triple bed"--