Design for archiving a sorted list (with ability for a few INSERT)
By all means use an unsigned int surrogate key as your primary, clustered index.  However, instead of using sequential values, build some padding into the sequence.  This means that you'll have to assign the id manually instead of using auto_increment.

If you use unsigned int in MySQL, the max value is 4,294,967,295.  If you expect to have at most 100,000 rows that means you could space each word out by more than 42,000.  

When you need to insert a word between two existing words, just plug it into the space half way between.  Let's say you use 40,000 as your intitial padding value.  If you have "house" at 800,000 and "dog" at 840,000 you can insert "nouveau" at 820,000.