Here are a few idioms that have preserved words that we no longer use by themselves. They are almost exclusively used in context, rather than stand-alone.
Eke is usually used as to 'eke out a living'. It comes from
an old verb meaning to add, supplement, or grow. It is also the
same word that gave us "eke-name" for additional name, which
Dint comes from the Old English where it originally
referred to a blow struck with a sword or other weapon. It is now
used as "by dint of something" where 'something' can stand for
charisma, hard work, or anything you can use to accomplish
Deserts, as in 'just deserts' comes from an Old French word
for 'deserve', and it was used in English from the 13th century to
mean that which is deserved. When you get your just deserts, you
get your due.
Fro, as in 'to and fro' comes from the old English way of
Kith, as in 'kith and kin' comes from an Old English word
referring to knowledge or acquaintance. The expression "kith and
kin" originally meant your country and your family, but later came
to have the wider sense of friends and family.
Umbrage, as in 'take umbrage' comes from the French ombrage
(shade, shadow), and it was once used to talk about shade from the
sun. It took on various figurative meanings having to do with
doubt and suspicion or the giving and taking of offense. To give
umbrage was to offend someone, to "throw shade".
Shrift, as in 'short shrift' came from the practice of
allowing a little time for the condemned to make a confession
before being executed. In that context, shorter was never better.