means Soft, thick, and full of crushed or mashed plant matter — the way fruit becomes when its flesh breaks down into a moist, fibrous mush.

from From "pulp," which comes through Old French "pulpe" from Latin "pulpa," meaning the soft fleshy part of fruit or flesh itself. The "-y" is the plain English suffix that turns a thing into the quality of being like it — so "pulpy" is simply "having the nature of pulp." The same root later flavored "pulp fiction," named for the cheap, soft wood-pulp paper those lurid stories were printed on.