Where does “тисяча” come from?
тисяча (Ukrainian) comes from Russian ты́сяча, from Old East Slavic тысяча, from Proto-Slavic tỳsęti, from Proto-Balto-Slavic *tū́ˀsantis, from Proto-Indo-European tuHsont-, from Proto-Indo-European tewh₂- — to swell; to crowd; to be strong.
тисяча (Ukrainian): thousand
Ancestry of “тисяча”, step by step