Origins
The word 'effort' carries the imagery of strength being pushed outward — a forceful exertion from within. Its etymology traces back through Old French to a Vulgar Latin construction that literally meant 'to force out,' combining the idea of outward motion with the idea of physical power.
Old French 'esfort' (exertion, force, strength) derived from the verb 'esforcier' (to force, to exert oneself), which came from Vulgar Latin *exfortiāre. This late Latin compound joins the prefix 'ex-' (out, forth) with 'fortis' (strong, powerful, brave). The literal image is of bringing one's strength to bear — pushing force outward from the body or mind toward a task.
Latin 'fortis' is one of the language's most important adjectives and the parent of an extensive English word family. 'Force' (from French 'force,' from Vulgar Latin *fortia, a noun derived from 'fortis'), 'fort' (a strong place), 'forte' (a strong point), 'fortify' (to make strong), 'fortress' (a stronghold), 'comfort' (to strengthen together — 'com-' + 'fortis'), and 'reinforce' (to strengthen again) all descend from this adjective.
Proto-Indo-European Roots
The PIE root *bʰerǵʰ- meant 'high' or 'elevated.' The semantic path from 'high' to 'strong' passes through the intermediate concept of a fortified hilltop — a high place that is therefore strong, defensible, powerful. This connection is preserved more transparently in the Germanic branch: PIE *bʰerǵʰ- produced Proto-Germanic *burgz (a fortified elevation), which became Old English 'burg' and Modern English 'borough,' 'burg,' and the '-bury' in place names like Canterbury and Glastonbury. German 'Burg' (castle, fortress) is the same word. So 'effort' (strength pushed outward) and 'borough' (a strong high place) are distant cousins, connected through the ancient association of height with strength.
English borrowed 'effort' from French in the late fifteenth century. Its initial uses described physical exertion — the effort of lifting, of fighting, of laboring. The extension to mental exertion followed naturally: intellectual effort, emotional effort, the effort of concentration. By the seventeenth century, 'effort' could refer to the product of exertion as well as the act itself: 'her latest effort' means 'the latest thing she produced through exertion.'
The word participates in several revealing collocations. A 'best effort' implies maximum exertion. 'Effortless' describes something done with apparent ease — where the strength is so great that no strain is visible. 'War effort' (coined in World War I) collectivized the concept: an entire nation's exertion directed toward a single goal. 'Effort' in physics has a technical meaning related to the force applied to a machine.
Latin Roots
In Italian, the cognate 'sforzo' (from the same Vulgar Latin source) gave music the term 'sforzando' — an instruction to play a note with sudden force, literally 'forcing it out.' This musical term perfectly captures the etymological meaning of 'effort': a concentrated push of energy.
The concept of effort has interested psychologists and economists as well as linguists. The psychologist Daniel Kahneman's distinction between 'System 1' (effortless, intuitive thinking) and 'System 2' (effortful, deliberate thinking) makes 'effort' a central category of cognitive science. In economics, 'effort' is a variable in labor theory — the intensity of work, as opposed to its duration.
From PIE *bʰerǵʰ- (high, strong) through Latin 'fortis' (powerful) to Old French 'esfort' (exertion) to Modern English 'effort,' the word traces the human experience of mobilizing internal strength for external tasks — the fundamental act of trying.