jaček = it is not a Czech word, even not a name, may be special name in some family closest may be "small yak" (sort of cattle) 8) what is the context?
Jač/Jáč (Jatsch) and Jaček/Jáček (Jatschek) are common surnames in the C.R. as well as in Germany/Austria (with the German spelling). jáček is a diminutive of jak (= yak)