Origins
The word 'exam' is a nineteenth-century clipping of 'examination,' which entered English around 1380 from Old French 'examinacion,' from Latin 'exāminātiōnem' (accusative of 'exāminātiō'), meaning 'a weighing, a consideration, a testing.' The Latin verb 'exāmināre' meant 'to weigh accurately, to test, to examine,' and its root noun 'exāmen' carried two seemingly unrelated meanings: the tongue or needle of a balance (the pointer that indicates the weight), and a swarm of bees. Both senses derive from the verb 'exigere' (to drive out), from 'ex-' (out) + 'agere' (to drive, to do).
The connection between a balance needle and a swarm requires some explanation. 'Exigere' meant 'to drive out,' and by extension 'to weigh precisely' (to drive the balance to its true point) and 'to demand' (to drive out what is owed). The 'exāmen' — the indicator on the scale — was the instrument that 'drove out' the truth about a weight. The bee-swarm sense arose because a swarm 'drives out' from the hive. It is the scale metaphor that produced 'examination': to examine someone is to place their knowledge on the balance and see what it truly weighs.
The PIE root behind 'agere' is *h₂eǵ- (to drive), one of the most fertile roots in the Indo-European family. Through Latin 'agere' and its many derivatives, it produced an enormous English vocabulary: 'agent' (one who drives or acts), 'agile' (able to move quickly), 'act' (a thing done), 'exact' (driven to precision, from 'exigere'), 'essay' (from Latin 'exagium,' a weighing — the same scale metaphor as 'exam'), 'exigent' (demanding, pressing), 'navigate' (to drive a ship), 'ambiguous' (driven both ways), and 'prodigal' (driving forth, squandering). Through Greek 'ágein' (to lead, to drive), the same root gave us 'pedagogue' (one who leads children), 'synagogue' (a gathering together), 'demagogue' (a leader of the people), and 'strategy' (the leading of an army).
Latin Roots
In medieval Latin, 'exāmināre' was used in both legal and academic contexts. A witness might be 'examined' (tested for truthfulness), just as a student might be 'examined' (tested for knowledge). The formal academic examination emerged in the medieval European universities, where oral disputation — the public defense of theses before a panel of masters — was the primary method of assessment. Written examinations did not become standard until the eighteenth and nineteenth centuries, when the expansion of education made individual oral testing impractical.
The clipped form 'exam' first appeared in student slang around 1848 and quickly became standard informal English. This kind of clipping — 'examination' to 'exam,' 'laboratory' to 'lab,' 'mathematics' to 'math' — is characteristic of institutional language, where frequently used polysyllabic words are worn down by daily use.
The metaphor of weighing persists in everyday language about examinations. We speak of 'weighing' evidence, of arguments that 'carry weight,' of 'measuring' ability. The Latin image of the balance, with the needle driven to its true point by the weight of what is placed upon it, remains the hidden architecture of how English thinks about testing and judgment. Every exam paper is, etymologically, a set of scales — and what is being weighed is not the paper but the mind of the person who sits before it.