Are there any other conlanging examples of this sort of thing? I know it's
quite common in the celtic languages.

In one of my languages, West Nindic (Isn't that just a terrible name?) I have
this feature .... tho, it is admittedly a Sindarin/Welsh inspired Elvish
language ... but what can you do?

As an example:
   Í da dhen o moniel nian no da rosnÍr
   "The man hears/listens to the music of the river"

  Í "is"
  da "the"
  dhen "man" (lenited form of den)
  o "at"
  moniel "hearing"  (verbal noun of mon-)
  nian "song"
  no "of" (originally "towards" < Nindic nodd)
  rosnÍr "river"  (lenited form of rhosnÍr)
(this originally meant "running water" < Nindic rhotha-neri)