Where does “шириться” come from?

шириться (Russian) comes from Russian ши́рить, from Serbo-Croatian širiti, from Slovene sir, from Proto-Slavic syrъ, from Proto-Balto-Slavic sū́ˀras, from Proto-Indo-European súHros — sour, acidic, salty.

шириться (Russian): to widen; to spread, to expand

Definitions

to widen; to spread, to expand

Ancestry of “шириться”, step by step

Step	Language	Word	Meaning
1	Russian	ши́рить	to widen
2	Serbo-Croatian	širiti	to widen; to expand; to spread
3	Slovene	sir	cheese
4	Proto-Slavic	syrъ	damp, raw
5	Proto-Balto-Slavic	sū́ˀras	salty, bitter
6	Proto-Indo-European	súHros	sour, acidic, salty

Every word from Proto-Indo-European súHros →Every word from Proto-Balto-Slavic sū́ˀras →Every word from Proto-Slavic syrъ →