Origins
The English word 'impend' entered the language in the late sixteenth century, borrowed directly from Latin 'impendere' (to hang over, to overhang, to be imminent). The Latin verb combines 'in-' (over, upon) and 'pendere' (to hang), producing the literal image of something hanging over — suspended above and threatening to fall.
The physical sense was vivid in Latin. Virgil used 'impendere' to describe cliffs overhanging the sea, rocks suspended over paths, and clouds hanging threateningly over the land. The word carried an inherent menace: what hangs over might fall. The transition from 'hanging over physically' to 'about to happen ominously' was natural and was already complete in classical Latin. Cicero used 'impendere' for dangers, wars, and calamities that loomed over the state.
In English, the physical sense was never very prominent. The word arrived primarily in its figurative form: impending danger, impending doom, impending crisis. The adjective 'impending' (present participle of 'impend') is far more common than the verb itself and has become the standard English word for 'about to happen, especially something bad.' One rarely says 'danger impends' but routinely says 'impending danger.'
Latin Roots
The menacing quality of 'impend' and 'impending' deserves attention. While 'imminent' (from Latin 'imminere,' to project over, also from 'in-' + a verb of positioning) can be neutral — an imminent arrival, an imminent announcement — 'impending' almost always implies threat. Impending doom, impending disaster, impending war, impending layoffs. The word has acquired a strongly negative prosody that its Latin ancestor did not necessarily carry. This narrowing of connotation has made 'impending' one of the most atmospheric words in English.
The connection to the broader 'pendere' family is illuminating. Where 'depend' is hanging down from (reliance), 'suspend' is hanging up (interruption), 'append' is hanging onto (addition), 'impend' is hanging over (threat). Each word takes the same physical action — hanging — and redirects it spatially, with each direction producing a different figurative meaning. Down produces reliance. Up produces interruption. Onto produces addition. Over produces menace.
The related Latin verb 'impendere' had a second meaning that produced a different English word. Besides 'to hang over,' it could mean 'to weigh out for' or 'to expend upon' — connecting to the 'weighing/paying' sense of 'pendere.' This secondary meaning did not pass into English through 'impend' but survives in related Latin legal terminology.
Modern Usage
In modern usage, 'impend' remains a literary and somewhat formal word. Journalists write of impending elections, impending regulatory changes, impending storms. Novelists use 'impending' to build atmosphere and dread. The word functions almost exclusively in serious contexts — one would never speak of an 'impending birthday party' without ironic intent. This tonal restriction makes 'impend' unusually precise: to use it is to invoke threat, weight, and the anxious sense of something heavy hanging directly overhead, about to drop.
The Sword of Damocles — the ancient Greek parable in which a single sword is suspended by a horsehair over a courtier's head during a banquet — is the perfect embodiment of what 'impend' literally means. The sword impends: it hangs over, it threatens, it could fall at any moment. Every use of 'impending' in English carries, at its etymological core, that image of a suspended blade.