/streɪn/
[noun] A force, pressure, or stress that stretches or damages something, or a particular type or variety of something, such as a plant, animal, or idea. The word can also describe a melody or the sound of music.
The word 'strain' secretly contains two completely different words that fused together over centuries — one about pulling tight, one about breeding.
The word 'strain' is one of English's most quietly fascinating words, because what looks like a single word is actually two entirely different words wearing the same coat. They arrived in English through different routes, gradually blurred together, and now sit comfortably sharing the same spelling and sound — a small etymological miracle hiding in plain sight.
The first strand comes from the Old French word 'estreindre', meaning 'to bind tightly' or 'to press together'. That Old French verb descended from the Latin 'stringere', which meant 'to draw tight', 'to press', or 'to bind'. Latin 'stringere' also gave English the word 'strict' (via Latin 'strictus', the past participle of 'stringere' → Old French 'estroit' → English 'strict'), and 'constrict' (Latin 'constringere' → English 'constrict'), and even 'stress' (from Latin 'strictus' → Old French 'estresse' → Middle English 'stresse'). By the time 'strain' entered Middle English in the 13th century from Old French 'estraindre', it carried the physical sense of pulling or stretching something to its limit — the strain of a rope, the strain on a muscle, the strain of effort.
The second strand is entirely different in origin. The sense of 'strain' meaning a breed, a lineage, or a variety — as in a strain of wheat, or a new strain of virus — comes from Old English 'streon', which meant 'gain', 'acquisition', or 'offspring'. This Old English word was related to the verb 'gestrienan', meaning 'to beget' or 'to acquire', and was used to describe family descent and hereditary lines. This sense survived quietly through Middle English, and by the 16th century it had settled into its modern meaning of a distinct variety or type within a species. When scientists today talk about a new strain of influenza, they are using a word that stretches back to the Anglo-Saxon idea of lineage and birth.
The musical sense of 'strain' — a melody, a passage of song, or a sustained note — arrived in the 16th century and appears to have grown from the idea of drawing out sound, of stretching music through time. Shakespeare used it beautifully, and writers of his era spoke of the 'strains' of a lute or a choir as naturally as we might speak of a tune today. This meaning likely branched from the 'tighten and draw' root, imagining the way a musician draws sound from a taut string.
What makes 'strain' particularly rich is how all of these meanings — physical tension, hereditary type, and musical passage — have remained active simultaneously for centuries. In any given paragraph, a writer could describe the strain of a long journey, a new bacterial strain, and the strains of a distant violin, and each usage would feel completely natural. Few English words carry such genuinely different histories in a single form, and yet manage to feel so unified, as if all the meanings were always meant to belong together.