I've often wondered about this. "Buchstabe" obviously(?) derives from the letters used in the early printing presses (think Gutenberg). What did they call a letter before Gutenberg?
update
Seems my assumption was wrong and it wasn't obvious after all. (Lucky that I added the question mark.) Thanks for the answers.
According to Wiktionary, the etymology of "Buchstabe" doesn't have anything to do with printing presses:
Herkunft: wahrscheinlich aus dem Germanischen: *bōks - Runenstäbchen (die unter Anderem aus Buchenholz gefertigt wurden) und *stab - senkrechter Strich in der Rune. (German wiktionary)
Etymology From Middle High German buochstap, from Old High German buohstab (“letter, writing”). From Proto-Germanic *bōkastabaz, from Proto-Indo-European roots *bʰagós (“book”) + *stěbʰ, *stemb (“support, stamp, be astonished”). Compare English bookstaff, bookstave. (English wiktionary)
This etymological explanation suggests that the word "Buchstabe" has been in use much longer than since the time of Gutenberg.
Simple answer: Buchstabe.
In ancient times, runes (the first letters in use for most Germanic languages) were carved into thin wood, often beech wood (German Buche).
The German words Buchstabe and Buch derive from the name of this tree, as does the English word "book". The same is true for the Nordic languages.
The word Buch was used for books already before they were printed.
