In the description of Jacques Kohn in the beginning of Isaac Bashevis Singer's "A Friend of Kafka", he's described as wearing this:
Although he still dressed in the style of a dandy, his clothes were shabby. He wore a monocle in his left eye, a high old-fashioned collar (known as "father-murderer"), patent-leather shoes, and a derby. He had been nicknamed 'the lord' by the cynics in the Warsaw Yiddish writers' club that we both frequented.
Googling "father-murderer" gets me some very disturbing results and not much about the collar known as the "Vatermörder", but apparently it is a high, stiff collar that sometimes killed the people wearing it.
So... why is Kohn wearing this sometimes-deadly collar? What do his clothing choices tell us about the character?