In this topic, Les raised the issue of
troth, which he felt should be rare on the grounds of being obsolete.
Nobody spoke up for it, but maybe it was overshadowed by
nimby and, mainly in another thread,
faerie. I found an example of its use in a
recent news item about a French "anti-separatism" law:
People representing the French state, in either the public or private sector, will have to plight their troth to the principles of secularism and neutrality in public service. One consequence is the end of public swimming pools with male and female-only lanes for religious reasons.
(It's good to see the French government is focused on the big issues of the day.)
When the word is used, it's usually being either pledged or plighted, or occasionally given. These are phrases which people have perhaps lifted from traditional wedding vows - which are possibly not heard so often these days in actual wedding ceremonies.
I don't think
troth is actually common, so it will be treated as a rare word from now on.