Why does the KJV say "people perish" in Pr. 29:18? Can anyone tell me why the KJV translates the Hebrew words yipara am as “people perish” in Pr. 29:18? (The Hebrew word am means people and yipara means unrestrained.) Other translations render yipara am as “the people run wild,” and “the people cast off restraint.” YLT says, “Without a Vision is a people made naked.” Brenton says, “There shall be no interpreter to a sinful nation: but he that observes the law is blessed.” The Lexham English Septuagint says, “A seer will never come to a lawless people, but those who keep the law are most blessed.” The JPS Tanakh: The Holy Scriptures according to the Masoretic Text (1917) translates yipara am as “the people cast off restraint.” What am I missing here?
The Clementine Vulgate has 


  Cum prophetia defecerit, dissipabitur populus ; qui vero custodit legem beatus est.


Which the Douay translates as 


  When prophecy shall fail, the people shall be scattered abroad: but he that keepeth the law is blessed. 


That's close enough to the KJV to suggest the possibility that they may have consulted the Vulgate to try and help understand perhaps a rare word. But then the question arises, why did the Vulgate translate it that way?  Its possible that its based on a Qere (i.e. Massoretic margin note reading) or alternative vowel pointing, but I don't know.

A search for יִפָּ֣רַֽע on Unbound Bible against the Westminster Leningrad Codex reveals that this word occurs only in this verse.  Searching without points יפרע reveals that it occurs also in Leviticus 21:10, where it says the high priest is to "not uncover his head."

The Geneva Bible (1599) also has


  Where there is no vision, the people decay: but he that keepeth the law is blessed.


And Matthew's Bible (1537)


  Wher no Prophete is ther the people perysh: but wel is hym that kepeth the law.


So that seems to have been the standard translation of this at that time.