Where does “suspicious” come from?

Suspicious comes from Old French sospecious, derived from Latin suspiciosus, meaning inclined to suspect or mistrust.

suspicious (English): Arousing suspicion; Distrustful or tending to...

Definitions

Step	Language	Word	Meaning
1	Old French	sospecious	—
2	Latin	suspiciosus	suspicious
3	Latin	suspiciō	—
4	Latin	suspicere	second-person singular present active subjunctive...
5	Latin	specere	present active infinitive of speciō;...
6	Latin	specio	I observe, watch, look at
7	Proto-Italic	spekjō	to observe, to see
8	Proto-Indo-European	spéḱyeti	to be looking at, to keep looking at
9	Proto-Indo-European	speḱ-	to see, to look, to observe