Where does “realist” come from?

Realist comes from English real, derived from Latin -ista and Latin regalis, which is built on Latin -alis from Proto-Indo-European h₃reǵ-.

realist (English): An advocate of realism; one who believes that...

Definitions

Step	Language	Word	Meaning
1	English	real	True, genuine, not merely nominal or apparent;...
2	Middle English	real	real, true, factual; concerning possessions;...
3	Old French	reel	—
4	Latin	reālis	real
5	Latin	rēs	thing, object, stuff
6	Latin	vindicatio	civil lawsuit; protection, defence; vindication;...
7	Latin	vindicō	to lay claim to as one's own (often with sibi)
8	Latin	vindex	claimant, vindicator
9	Latin	dīcō	to say, talk, speak, utter, mention
10	Latin	-tiō	tion, -ation, -ing
11	Latin	dissertātiō	(spoken) dissertation, discourse, disquisition
12	Latin	dissertus	arranged, disposed; explained
13	Latin	disserere	second-person singular future passive indicative...
14	Latin	dis-	asunder, apart, in two; reversal, removal;...
15	Latin	calceus	shoe
16	Latin	calx	limestone; chalk; the finish line
17	Ancient Greek	χάλιξ	small stone, pebble; gravel, rubble