Yes. But you'd be hard-pressed to pin a precise number on him.

See Frances Emberson MARK TWAIN'S VOCABULARY (1935) and Ramsay and
Emberson's A MARK TWAIN LEXICON (1938, but reprinted in the 1960s).

There are 7,802 entries in LEXICON and 3,384 are not found in OED. But many
of these are found in other dictionaries. Another 958 words Twain used are
found in OED, but Twain's use of them precedes any uses cited by OED. So,
the total is 4,342, but you can't claim these as words invented by Twain.
Some are old words used by Twain in new ways, etc.

I could bullyrag about this, but it would give me the fan-tods. I don't know
what you'd have to pungle to obtain copies, but consult these two sources
directly.

Kevin Mac Donnell
Austin TX