I'm trying to make a backup copy of some table, but I keep getting the following error:

*******************************************
SQL-query:

INSERT INTO `phpbb_search_wordlist`
VALUES (
'fianc', 5703, 0
)

MySQL said: Documentation

#1062 - Duplicate entry 'fianc' for key 1
*******************************************

As I check the row that has "fianc" and several rows that are in the neighborhood (after I sort in ascending order), I see these rows

fewer 2091 0
fianc 5703 0
fiancee 4978 0
fiancée 4592 0
fiber 2859 0
fibre 14062 0
ficticious 3182 0

As you can see, there is no duplicate entry. What's going on here? What is causing the problem and how can I fix it or get around it?