Where does “sōm” come from?

sōm (Silesian) comes from Old Polish sam, from Proto-Slavic samъ, from Proto-Balto-Slavic *sāmas, from Proto-Indo-European somHós, from Proto-Indo-European sem- — together, one.

sōm (Silesian): alone

Definitions

alone

Ancestry of “sōm”, step by step

Step	Language	Word	Meaning
1	Old Polish	sam	alone, by oneself, without company
2	Proto-Slavic	samъ	self, oneself
3	Proto-Balto-Slavic	*sāmas	—
4	Proto-Indo-European	somHós	same, alike
5	Proto-Indo-European	sem-	together, one

Every word from Proto-Indo-European sem- →Every word from Proto-Indo-European somHós →Every word from Proto-Balto-Slavic *sāmas →