@MilesMeraki got the correct answer of "to", however I think the SPAM system has hidden the post.
"to" has occurred 361134 times
"327879" has occurred 327879 times
"a" has occurred 317993 times
Answers found with:
find . -type f -exec html2text -nobs {} + | tr '[:space:]' '[\n*]' | grep -v "^\s*$" | sort | uniq -c | sort -bn