According to Godrom’s “Deutsches Namenlexikon” the name “Prokosch” is indeed very old and known to have existed since the 14th century.
Prokosch, also Proksch, Broksch, Prokop and Prokopf from St Prokop the patron saint of ancient Bohemia. It is a first name. This name is quite prolific in Vienna, Austria, and is recorded in early times as Procop Moelner 1447 Glatz, Procoff Funke 1532 Goerlitz, Silesia, Brocuff Rotbart 1505 Freystadt.
Czech, Polish, Ukrainian, and Belorussian: from the personal name Prokop, Greek Prokopios, from pro ‘before’, ‘in front’ + kopē ‘cut’, originally an omen name meaning ‘success’, ‘prosperity’ but as a Church name taken to mean ‘pioneer’, as it was the name of the first victim of Diocletian’s persecutions in Palestine in AD 303. He is venerated in the Orthodox Church, whence the popularity of the Russian personal name Prokofi. The popularity of the name in central Europe is largely due to a later St. Prokop, patron saint of Bohemia, who founded Sázava abbey in Prague in the 11th century.
Point of interest on research:
Professional researchers extract information and names from old records and include it in the Lexicon. A note to remember, during the 30 Year War, the European population was reduced by 50%, due to the Bubonic Plague and it was up to 80 % in Bohemia. The 30 Year War was a religious war between Catholics and Protestants, with the Swedes supporting the Protestants. Most of the Catholic churches were burned and vice versa. It is difficult to find records before the 30 Year War, which was between 1618 and 1648. This explains why many researchers eventually hit a dead end and the end of any records. When professional name researchers cannot follow the family surname trail because of missing church registers, they look into the legal records which sometimes reveal ancestral information, and these are included in the Lexicon.