Nearly everywhere, this would be a misprint, either for “crops” or “corpse.”  But not in this text:

Life, he himself said once, (his biografiend kills him, in fact, verysoon, if yet not, after), is a wake, livit or krikit, and on the bunk of our breadwinning lies the cropse of our seedfather . . .

For Finnegans Wake, his fantasy about the mighty combining power of the dreaming imagination, James Joyce invented an artificial language.  It is based on multilingual puns, creative misspellings, and what in Through the Looking-Glass Lewis Carroll called portmanteau words, that is, combinations like “biografiend,” which packs “biographer” and “fiend” into the same verbal suitcase in order to denigrate biographers.  Reading Wakespeak can be fiendishly difficult, especially when passages from the book are taken out of context, and I do not intend to interpret the two lines above except to say that “seedfather” denotes Adam, father of mankind, and in particular the Adam whose expulsion from the Garden of Eden resulted in mankind’s need to grow food (“breadwinning”), and hence a need for seed.  “Cropse” suggests both the “crops” which seeds produce and the “corpse” or body of Adam, whose expulsion also, we are told, brought death into the world.

The word “crops” comes from ancient Germanic terms meaning “head or top part” of a plant, say an ear of wheat, which is of course the part harvested to produce crops.  “Corpse” derives from the Latin corpus, “body.”  So the words are completely unrelated, except as Joyce brings them together in a neologism succinctly expressing one of the main themes of Finnegans Wake, which is (to simplify) that fecundating corpses may give rise to new crops, that you cannot separate death from life, that endings circle around to beginnings.  The title of Joyce’s book refers to the “wake” mourning the death of the Irish laborer Tim Finnegan but is also an instruction to all the Finnegans of the world to “wake up!,” as indeed Tim Finnegan wakes up when mourners sprinkle whiskey (“water of life” in Gaelic) over his body.

One more meaning of “corpse”: as a verb in British theatrical slang, it means to mess up your own or another actor’s performance (thus creating a fiasco) by forgetting your lines or especially by breaking out into laughter at the wrong moment.  No one knows for sure where this usage comes from, though it may go back to an instance when an actor playing a corpse onstage just could not lie deathly still but instead broke out into lively laughter . . . an etymology which would greatly have pleased James Joyce.