'Spectacle' is Latin for 'a public show' — from 'spectare' (to watch). 'Spectacles' = tools for looking.
A visually striking performance or display; an event or scene regarded as impressive or noteworthy; (plural 'spectacles') a pair of eyeglasses.
From Old French 'spectacle' (a sight, a show, a public display), from Latin 'spectāculum' (a show, a spectacle, a public performance, an arena), from 'spectāre' (to watch, to look at, to observe, to behold), the frequentative form of 'specere' (to look at, to see), from PIE *speḱ- (to observe, to look at, to watch). The PIE root is extraordinarily productive: it generated Latin 'specere' and its vast family — 'spectator' (one who watches), 'specimen' (something to look at), 'species' (appearance, kind), 'special' (of a particular kind), 'specific,' 'spectrum' (an appearance, a vision), 'speculate' (originally to observe from a watchtower), 'suspect' (to look at from below, i.e., with suspicion), 'inspect
The word 'spectacles' for eyeglasses dates to the 15th century — making it one of the oldest English words for the device. The logic was simple: spectacles are instruments for 'spectating,' for looking at things more clearly. In British English, 'spectacles' remains the formal word for glasses.