I have the Oxford/LOA INNOCENTS ABROAD e-text.  The result of the
search for tabu, taboo follows.  The page numbers given refer to
the first edition of IA and the keyword has been capitalized to
make it easier to find within the text:

Contents Page xvii

[Chapter LIX.

Going Home--A Demoralized Note-Book--A Boy's Diary--Mere Mention of Old
Spain--Departure from Cadiz--A Deserved Rebuke--The Beautiful
Madeiras--TABOOED--In the Delightful Bermudas--An English
Welcome--Good-by to "Our Friends the Bermudians"--Packing Trunks
for Home--Our First Accident--The Long Cruise Drawing to a Close--At
Home Amen]

Chapter LI. (pg. 538)

I have set these extracts down, as I found them. Every where, among the
cathedrals of France and Italy, one finds traditions of personages that
do not figure in the Bible, and of miracles that are not mentioned in
its pages. But they are all in this Apocryphal New Testament, and
though they have been ruled out of our modern Bible, it is claimed that
they were accepted gospel twelve or fifteen centuries ago, and ranked
as high in credit as any. One needs to read this book before he visits
those venerable cathedrals, with their treasures of TABOOED and
forgotten tradition.

Chapter LII. (pg. 551)

Shechem is distinguished as one of the residences of the patriarch
Jacob, and as the seat of those tribes that cut themselves loose from
their brethren of Israel and propagated doctrines not in conformity
with those of the original Jewish creed. For thousands of years this
clan have dwelt in Shechem under strict TABU, and having little
commerce or fellowship with their fellow men of any religion or
nationality.

Kevin B.