Where does “kaksossisko” come from?

kaksossisko (Finnish) comes from Finnish Sisko, from Finnish sisar, from Proto-Finnic sesar, from Proto-Balto-Slavic swésō, from Proto-Indo-European swésōr, from Proto-Indo-European su-h₁ésh₂-ōr, from Proto-Indo-European h₁ésh₂r̥ — blood.

kaksossisko (Finnish): twin sister

Definitions

twin sister

Ancestry of “kaksossisko”, step by step

kaksossisko traces back through two separate lines of ancestry.

via Finnish Sisko

Step	Language	Word	Meaning
1	Finnish	Sisko	sister
2	Finnish	sisar	sister
3	Proto-Finnic	sesar	sister
4	Proto-Balto-Slavic	swésō	sister
5	Proto-Indo-European	swésōr	sister
6	Proto-Indo-European	su-h₁ésh₂-ōr	—
7	Proto-Indo-European	h₁ésh₂r̥	blood

via Finnish kaksonen

Step	Language	Word	Meaning
1	Finnish	kaksonen	A twin; When used as modifier in compound terms...
2	Finnish	kaksi	two
3	Proto-Finnic	kakci	two
4	Proto-Uralic	*kakta	—

Every word from Proto-Indo-European h₁ésh₂r̥ →