Where does “spectro-” come from?

spectro- (English) comes from English Spectrum, from Latin spectrum, from Ancient Greek σκοπέω, from Ancient Greek σκοπός, from Ancient Greek σκέπτομαι, from Proto-Hellenic sképťomai, from Proto-Indo-European spéḱyeti, from Proto-Indo-European speḱ- — to see, to look, to observe.

spectro- (English): optical spectra

Definitions

optical spectra

Ancestry of “spectro-”, step by step

Step	Language	Word	Meaning
1	English	Spectrum	A range; a continuous, infinite, one-dimensional set, possibly bounded by extremes
2	Latin	spectrum	appearance, image; apparition, specter
3	Ancient Greek	σκοπέω	I look, look at, behold; I examine, inspect; 413...
4	Ancient Greek	σκοπός	watcher, lookout; protector, guardian; spy, scout
5	Ancient Greek	σκέπτομαι	I look at, examine; I examine, consider, think
6	Proto-Hellenic	sképťomai	to look at
7	Proto-Indo-European	spéḱyeti	to be looking at, to keep looking at
8	Proto-Indo-European	speḱ-	to see, to look, to observe

Words derived from “spectro-”

Every word from Proto-Indo-European speḱ- →Every word from Proto-Indo-European spéḱyeti →Every word from Proto-Hellenic sképťomai →