invoke

To invoke is to call something into being through the power of the voice.‌​‌​‌​‍​‍​‍​‍​‍​‍​‍​‌​‌​‌​‍​‍​‌​‍​‌​‌​‍​‍​‌​‍​‌​‌​‍​‌​‍​‌​‌​‍​‌ The word belongs to one of the richest etymological families in Latin — the family of 'vox' (voice) and 'vocāre' (to call) — and it preserves the ancient belief that naming a power could summon it.

English borrowed 'invoke' in the late fifteenth century from Old French 'invoquer,' from Latin 'invocāre' (to call upon, to appeal to, to pray to), formed from 'in-' (upon, towards) + 'vocāre' (to call, to summon, to name). Latin 'vocāre' derives from 'vōx' (voice, genitive 'vōcis'), which comes from PIE *wekʷ- (to speak, to voice).

The PIE root *wekʷ- generated two major branches. Through Latin 'vōx' and 'vocāre,' it produced an enormous family: 'voice,' 'vocal,' 'vowel' (from 'vōcālis littera,' a voiced letter), 'vocabulary' (the words one can voice), 'vocation' (a calling), 'advocate' (one called to speak for another), 'provoke' (to call forth — originally to challenge), 'revoke' (to call back), 'evoke' (to call out), 'convoke' (to call together), and 'equivocal' (calling equally in two directions — ambiguous). Through Greek, the same root produced 'epos' (word, song — the root of 'epic'), 'ἔπος' giving rise to 'epic' (originally a spoken narrative poem, as opposed to lyric poetry accompanied by the lyre).

The religious sense of 'invoke' is the oldest and most literal. In Roman religion, 'invocāre' was the formal act of calling upon a god for assistance. Prayers, rituals, and sacrifices all contained invocations — the naming of the deity whose attention was sought. This practice was not unique to Rome. The Sanskrit cognate 'vāk' (speech, voice) was personified as the goddess Vāc, the deity of sacred speech, reflecting the Indo-European belief that the voice itself had divine power.

The literary invocation descends directly from this religious practice. The convention of beginning an epic poem with an invocation to the Muse — 'Sing, O goddess' in Homer, 'Arms and the man I sing' in Virgil, 'Of man's first disobedience... sing, Heavenly Muse' in Milton — was not mere ornament. It was a formal request for divine assistance, an acknowledgment that the poet's voice alone was insufficient for the task.

The legal sense of 'invoke' — to cite a law, precedent, or right — emerged by the seventeenth century. To invoke one's Fifth Amendment rights, to invoke a clause in a contract, to invoke precedent in a court argument — these uses retain the core meaning of calling upon an authority for protection or support. The authority invoked is not a god but a legal principle, yet the rhetorical structure is identical: name the power, and it comes to your aid.

In computing, 'invoke' acquired a technical meaning in the late twentieth century: to call a function, method, or procedure — to cause it to execute. A programmer 'invokes' a function the way a priest invokes a deity: by naming it correctly, with the right parameters, and expecting a defined response. The metaphor is remarkably apt, and the computing usage has become so common that for many people it is now the primary sense of the word.