Where does “cieniutko” come from?

cieniutko (Polish) comes from Polish cieniutki, from Polish cienki, from Proto-Slavic tьnъkъ, from Proto-Indo-European ténh₂us, from Proto-Indo-European tenh₂-, from Proto-Indo-European ten- — to stretch, to extend.

Ancestry of “cieniutko”, step by step

Step	Language	Word	Meaning
1	Polish	cieniutki	—
2	Polish	cienki	thin; inept; mediocre; weak; lame
3	Proto-Slavic	tьnъkъ	thin
4	Proto-Indo-European	ténh₂us	thin
5	Proto-Indo-European	tenh₂-	to stretch, to extend
6	Proto-Indo-European	ten-	to stretch, to extend

Every word from Proto-Indo-European ten- →Every word from Proto-Indo-European tenh₂- →Every word from Proto-Indo-European ténh₂us →