A few horse words in Old Polish describing a pacing horse

Salve amici,
the year is drawing to an end so allow me to talk about some horse 'things'  long neglected. i.e., my blogging.
  in the XVI-XVIII century Polish writings  these words - ''stupak,'' ''stępak,'' ''szłapak'' - often appear to describe for a certain kind of a riding horse.
Samuel Bogumił Linde in his monumental work ''Słownik jẹzyka polskiego'' (Dictionary of Polish Language , 1812 AD) vol. 5, page 415 explains 'stępak' as a pacing horse/caballo de paso (in XIX century Polish a 'jednochodnik,' now it is 'inochodziec'). In the older Medieval sources: Latin ''pro equo ambulatore/ambulato''these names were used as palefroi (French)/palfrey(English),  podjezdek/stępak (Polish).
 Perhaps it is worth mentioning that in 1392 King Władysław Jagiellon paid 21 grzywna for a ''stepak'' (ambulator in the sources) and gave this horse to the Masovian duke Siemovit's wife as a gift...

Well, let us look at some sources from XVI-XVIII centuries:

 ...in 1596 AD Vatican envoy segnor Vannozzi visitng chancellor Jan Zamoyski always had been given 'tarant'(an appaloosa) 'stępak'  to ride to his estates, so when he finally left Poland the chancellor had given him the same horse with a saying:... equum graduarium, ut commodius possem redire in Italiam (a pacing horse, so I would return to Italy comfortably).

when the Polish embassy of Lew Sapieha came to Muscovy in 1600, his secretary Eiljasz Pielgrzymowski wrote a diary of that mission (delicate one as less than a decade later  Polish-Lithuanian Commonwealth would enter into war against the Muscovy Russia)- the embassy members gave Tsar Boris' son Fiodor, amongst many other horses and valuable gifts, two pacing horses:  a ''koń cisawy drygant stupak'' - chestnut pacing stallion (''drygant'' in Polish besides being a stallion could signify a very spirited mount) and a ''koń Turecki stupak siwy'' - grey Turkish pacing horse.

Let us jump almost a century and a half, to 1744, when another Polish writer, Marcin Matuszewicz (author of Memoirs of 1714-1765), noted that ''podobał się królowi* koń brata mego, szłapak brudno szpakowaty, za którego dałem w Wysokiem dukatów szesnaście; kazał go sobie król przejeżdżać na dziedzińcu i kazał zapłacić za niego 5o dukatów. Był ten koń faworytem królewskim i już potem król oprócz tego konia na innym nie jeździł...'' 
(the King* liked my brother's horse, dirty dark-grey pacing horse, I had paind 16 dukats for it in Wysokie, the king ordered the horse ridden in the courtyard and ordered to pay 50 dukats for him. This horse was the king's favorite and after that the king would not ride any other horse than this one...) 

*
the king in question is Augustus III of Poland 
ps
the two images above show training of the stepping/pacing horse, the first image is from 1680s and the second is from the second half of XVI century. The last horse image is a fabulous grey Spanish stallion, painted in the early XVIII century.