I was curious why a number of names in Navi- the prophets- seem to change. Yirmiyah is also called Yirmiyahu, Yeshayah/Yeshayahu, etc. and a number of the kings have a similar variation. Is there a reason for this, or a pattern as to which names are used when?
In the Navi as a rule Yirmiya is called Yirmiyahu, Yeshaya, is called Yeshayahu, etc. Common practice is to use the truncated version is speech. Although I'm not certain that there is really any difference than the way we shorten names bizman hazeh (nowadays), I think it may be due to Aramaic influence/pronunciation.
(A quick glance in the Targum gave a couple examples where the shortened version was used, although this wasn't always the case...and I only looked at a couple of places)