Where does “ușișoară” come from?

ușișoară (Romanian) comes from Romanian ușă, from Vulgar Latin ustia, from Latin Ostia, from Latin ōs, from Proto-Italic ōs, from Proto-Indo-European h₃ésth₁ — bone.

Ancestry of “ușișoară”, step by step

Step	Language	Word	Meaning
1	Romanian	ușă	door
2	Vulgar Latin	ustia	—
3	Latin	Ostia	Ostia
4	Latin	ōs	mouth
5	Proto-Italic	ōs	mouth
6	Proto-Indo-European	h₃ésth₁	bone

Every word from Proto-Indo-European h₃ésth₁ →Every word from Proto-Italic ōs →Every word from Latin ōs →