Right, this runs like a dog and is limited to working with a single delimiter, but hopefully will give you an idea.
SELECT aWord, COUNT(*) AS WordOccuranceCount
FROM (SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(concat(SomeColumn, ' '), ' ', aCnt), ' ', -1) AS aWord
FROM SomeTable
CROSS JOIN (
SELECT a.i+b.i*10+c.i*100 + 1 AS aCnt
FROM integers a, integers b, integers c) Sub1
WHERE (LENGTH(SomeColumn) + 1 - LENGTH(REPLACE(SomeColumn, ' ', ''))) >= aCnt) Sub2
WHERE Sub2.aWord != ''
GROUP BY aWord
ORDER BY WordOccuranceCount DESC
LIMIT 10
This relies on having a table called integers with a single column called i with 10 rows with the values 0 to 9. It copes with up to ~1000 words but can easily be altered to cope with more (but will slow down even more).
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