Origins
The word 'concern' has one of the most convoluted semantic histories in English, but at its etymological core, it is a word about sifting.โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโ Latin 'cernere' meant 'to sift,' 'to separate,' 'to distinguish,' and by extension 'to perceive' and 'to decide' โ all activities that involve sorting one thing from another. The compound 'concernere' (with 'con-,' meaning 'together') originally meant 'to sift together' or 'to mingle,' but in Medieval Latin it shifted to mean 'to relate to' or 'to regard' โ how things mix and mingle with one another, how they are relevant to each other.
The word entered English through Middle French 'concerner' in the fifteenth century, initially meaning 'to relate to' or 'to have to do with.' This neutral relational sense persists in phrases like 'as far as I'm concerned' and 'all concerned parties.' The emotional sense โ worry, anxiety โ developed by the seventeenth century, reflecting a natural progression: if something 'concerns' you (is relevant to you), it may well 'concern' you (cause you worry).
The PIE root *krey- (to sieve, to separate) is the ancestor of one of the most intellectually important word families in Western languages. The fundamental metaphor is that judgment is an act of separation โ sorting the significant from the insignificant, the true from the false, the good from the bad.
Latin Roots
In the Latin branch, 'cernere' produced 'discernere' (to separate apart โ hence 'discern,' to perceive distinctions), 'decernere' (to decide, to separate officially โ hence 'decree'), 'secernere' (to separate away โ hence 'secret,' something set apart from knowledge), 'certus' (determined, settled, separated and decided โ hence 'certain' and 'certify'), and 'discretus' (separated, distinguished โ hence 'discrete' and 'discreet,' which were originally the same word).
In the Greek branch, the same PIE root produced 'krinein' (to separate, to judge, to decide), which generated an extraordinary cluster of English borrowings. 'Crisis' (from 'krisis,' a separation, a decision, a turning point) is the moment when a situation separates into one outcome or another. 'Critic' (from 'kritikos,' able to judge) is one who separates good from bad. 'Criterion' (from 'kriterion,' a means of judging) is the standard by which separation is made. 'Crime' came through Latin 'crimen' (accusation, fault), possibly from Greek 'krima' (judgment, decision). 'Hypocrite' (from 'hypokrites,' one who judges beneath, i.e., an actor, one who pretends) rounds out this remarkable family.
The Germanic descendant of *krey- is less obvious but equally present. Old English 'hriddel' (a sieve) became modern English 'riddle' (in the sense of a coarse sieve, as in 'riddled with holes'). The more familiar sense of 'riddle' (a puzzle) comes from a different root.
Later History
The business sense of 'concern' โ as in 'a going concern' (a functioning business) โ dates from the eighteenth century and uses the relational meaning: a concern is an entity in which various parties have an interest (are concerned). The phrase 'going concern' originally meant 'a concern that is going on,' i.e., operating.
The emotional sense of 'concern' occupies a middle ground between 'interest' and 'worry.' To be 'concerned about' something is stronger than being 'interested in' it but weaker than being 'anxious about' it. This measured quality may explain why 'concern' has become the preferred term in diplomatic and institutional language: to 'express concern' acknowledges a problem without escalating to alarm.