Where does “sacrospinal” come from?

sacrospinal (English) comes from English spinal, from Latin spīnālis, from Latin spīna, from Proto-Italic speinā, from Proto-Indo-European spēy- — to stretch; thrive; succeed.

sacrospinal (English): Of, relating to, or affecting the sacrum and the...

Definitions

Of, relating to, or affecting the sacrum and the...

Ancestry of “sacrospinal”, step by step

Step	Language	Word	Meaning
1	English	spinal	Of or relating to the spine; Having a pithed...
2	Latin	spīnālis	of or belonging to the spine; spinal
3	Latin	spīna	a thorn or a thorny tree or shrub, such as whitethorn, hawthorn, or blackthorn
4	Proto-Italic	speinā	thorn
5	Proto-Indo-European	spēy-	to stretch; thrive; succeed

Every word from Proto-Indo-European spēy- →Every word from Proto-Italic speinā →Every word from Latin spīna →