It is a rather typical failure that a typo in the slave name leads to the fact that Jenkins simply cannot find the slave.

It is rather strange that Jenkins 1.514 says this type of problem is "unknown" to him, and it might be a bug in Jenkins:

Connecting to Jenkins-Slave-4-34
ERROR: Unexpected failure ... Possibly it is a bug in Jenkins. (previous text translated from German L10N)
java.net.UnknownHostException: Jenkins-Slave-4-34
at java.net.InetAddress.getAllByName0(InetAddress.java:1201)
at java.net.InetAddress.getAllByName(InetAddress.java:1128)
at java.net.InetAddress.getAllByName(InetAddress.java:1064)
at java.net.InetAddress.getByName(InetAddress.java:1014)
at hudson.os.windows.ManagedWindowsServiceLauncher.launch(ManagedWindowsServiceLauncher.java:202)
at hudson.slaves.SlaveComputer$1.call(SlaveComputer.java:223)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:636)

As the problem is really typical, I follow Jenkins' advice and report this as a bug. An UnknownHostException should not be "unknown" to Jenkins.