cool
i would think in the database. Have a table for words bit like:
Id
Name
English
French
German
sort of thing.
then in the templates have a system like %open_thread% or something like that (seperating actual template inclusion to these word inclusion). Something like that? the name field is extra so it is easier to know what it is going to be replaced by but you could just do it witn the ID number instead.
Would be very useful i have to say.