Where does “supination” come from?

Supination comes from Latin supinatio, derived from supinus meaning "lying backwards," ultimately from Proto-Indo-European -ti- and -tis noun-forming suffixes.

supination (English): The act or state of lying face upward, on one's...

Definitions

The act or state of lying face upward, on one's...

Ancestry of “supination”, step by step

supination traces back through two separate lines of ancestry.

via English supine

Step	Language	Word	Meaning
1	English	supine	Lying on its back; Reluctant to take action due...
2	Latin	supīnus	lying down with face upwards; supine, on one's back
3	Proto-Indo-European	upó	under, below
4	Proto-Indo-European	h₃ewp-	—

via Latin supino

Step	Language	Word	Meaning
1	Latin	supino	dative masculine singular of supīnus; dative...
2	Latin	-ō	suffixed to nouns or adjectives. Originally a-stem nouns. Later extended to nouns with other stems. Forms regular first-conjugation verbs
3	Proto-Indo-European	-ō	Derives nouns from roots

Words derived from “supination”

Every word from Proto-Indo-European h₃ewp- →Every word from Proto-Indo-European upó →Every word from Latin supīnus →