"Spatium" vs. "Space"
Layout → Page Settings calls it "Space"
Inspector for Images calls it "Spatium" (as does the disabled dialog for OMR and one translator hint)
I think "Space" is the term to use in English (but Spatium in German).
So I've made this part of PR #1385
Or call it "staff space", like SMuFL (or "stave-space", like Gould)?
On IRC I've been asked to poll for opinions here...